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Abstract:

Heat-expandable microspheres having high heat resistance and high solvent
resistance, a production process thereof include a shell of a
thermoplastic resin and a thermally vaporizable blowing agent being
encapsulated therein. The thermoplastic resin includes a copolymer
produced by polymerizing a polymerizable component containing a
carboxyl-group-containing monomer. The surface of the heat-expandable
microspheres is treated with an organic compound containing a metal of
the Groups from 3 to 12 in the Periodic Table.

Claims:

1. Heat-expandable microspheres, each comprising a shell of a
thermoplastic resin and a thermally vaporizable blowing agent being
encapsulated therein, wherein the thermoplastic resin comprises a
copolymer produced by polymerizing a polymerizable component comprising a
carboxyl-group-containing monomer, and the surface of the heat-expandable
microspheres is treated with an organic compound containing a metal of
the Groups from 3 to 12 in the Periodic Table.

2. Heat-expandable microspheres according to claim 1, wherein the
metal-containing organic compound is a metal-amino acid compound and/or a
compound having at least one bond represented by the following chemical
formula (1), M-O--C (1) (where "M" is an atom of a metal of the Groups
from 3 to 12 in the Periodic Table; and the carbon atom, "C", bonds to
the oxygen atom, "O", and also bonds only to a hydrogen atom and/or a
carbon atom except the oxygen atom, "O").

3. Heat-expandable microspheres according to claim 1, wherein the
metal-containing organic compound is soluble in water.

4. Heat-expandable microspheres according to claim 1, wherein the amount
of the metal ranges from 0.05 to 15 weight percent of the heat-expandable
microspheres.

5. Heat-expandable microspheres according to any claim 1, wherein the
metal belongs to the Groups 4 and 5 in the Periodic Table.

6. Heat-expandable microspheres according to claim 1, wherein the amount
of the carboxyl-group-containing monomer is greater than 50 weight
percent of the polymerizable component.

7. Heat-expandable microspheres according to claim 1, wherein the
polymerizable component further comprises a nitrile monomer.

8. Heat-expandable microspheres according to claim 1, wherein the. ranges
of the variation in the expansion-initiating temperature and maximum
expansion temperature of the heat-expandable microspheres after
dispersing 5 parts by weight of the microspheres in 100 parts by weight
of deionized water are each not greater than 10 percent of the
temperatures before the dispersion.

9. Heat-expandable microspheres comprising a shell of a thermoplastic
resin and a thermally vaporizable blowing agent being encapsulated
therein: wherein the thermoplastic resin comprises a copolymer produced
by polymerizing a polymerizable component comprising a
carboxyl-group-containing monomer; the maximum expansion ratio of the
heat-expandable microspheres is at least 30 times; and the ranges of the
variation in the expansion-initiating temperature and maximum expansion
temperature of the heat-expandable microspheres after dispersing 5 parts
by weight of the microspheres in 100 parts by weight of deionized water
are each not greater than 10 percent of the temperatures before the
dispersion.

10. Heat-expandable microspheres according to claim 1, wherein the
blowing agent comprises a hydrocarbon having a boiling point at least -20
deg. C. and lower than 170 deg. C. and a hydrocarbon having a boiling
point ranging from 170 deg. C. to 360 deg. C.

11. Heat-expandable microspheres according to claim 1, wherein the ratio
of DMF-insoluble matter contained in the heat-expandable microspheres is
at least 75 weight percent.

12. Heat-expandable microspheres according to claim 1, wherein the
maximum expansion temperature and maximum expansion ratio of the
heat-expandable microspheres are at least 240 deg. C. and at least 30
times, respectively.

13. Heat-expandable microspheres according to claim 1, being wet with a
liquid.

14. A process for producing heat-expandable microspheres comprising a
step of: treating the surface of base-material microspheres with an
organic compound containing a metal of the Groups from 3 to 12 in the
Periodic Table: wherein the base-material microspheres comprise a shell
of a thermoplastic resin produced by polymerizing a polymerizable
component comprising a carboxyl-group-containing monomer and a thermally
vaporizable blowing agent being encapsulated therein.

15. A process for producing heat-expandable microspheres according to
claim 14, wherein the surface treatment is carried out by mixing the
base-material microspheres and the metal-containing organic compound in
an aqueous dispersion medium.

16. A process for producing heat-expandable microspheres according to
claim 14, the process further comprising, prior to the surface-treatment
step, a step of: producing base-material microspheres by polymerizing the
polymerizable component in an aqueous dispersion medium in which an oily
mixture containing the polymerizable component and a blowing agent is
dispersed; wherein the surface treatment is carried out in the liquid
after the polymerization in which the base-material microspheres are
contained.

17. A process for producing heat-expandable microspheres according to
claim 14, wherein the surface treatment is carried out by spraying a
liquid comprising the metal-containing organic compound to the
base-material microspheres.

18. A process for producing heat-expandable microspheres of claim 14, the
process further comprising a step of wetting, with a liquid, the
heat-expandable microspheres produced at the surface treatment step.

19. Hollow particulates produced by heating and expanding the
heat-expandable microspheres of claim 1 and/or the heat-expandable
microspheres produced in the process of claim 14.

20. A composition containing at least one particulate material selected
from the group consisting of the heat-expandable microspheres of any one
of claim 1, the heat-expandable microspheres produced in the process of
claim 14 and the hollow particulates of claim 19; and a base component.

21. A formed product produced by forming the composition of claim 20.

Description:

TECHNICAL FIELD

[0001] The present invention relates to heat-expandable microspheres and a
method of making heat-expandable microspheres and application thereof.
Specifically, it relates to heat-expandable microspheres having high heat
resistance and high solvent resistance, a process for producing the same,
and application thereof.

TECHNICAL BACKGROUND

[0002] Heat-expandable microspheres, which comprise a shell of a
thermoplastic resin and a blowing agent encapsulated therein, are
generally called heat-expandable microcapsules. The thermoplastic resin
usually includes vinylidene chloride copolymers, acrylonitrile
copolymers, and acrylic acid ester copolymers. The blowing agent mainly
employed includes hydrocarbons, such as isobutane and isopentane. (Refer
to Patent Reference 1).

[0003] An example of such heat-expandable microcapsules already is
disclosed as heat-expandable microspheres comprising a shell of a
copolymer produced by polymerizing (I) a nitrile monomer and (II) a
carboxyl-group-containing monomer. (Refer to Patent Reference 2).
Although the heat-expandable microcapsules have good heat resistance, a
higher grade of heat resistance is required to meet the recent demand for
better microcapsule properties.

[0004] A variant of similar heat-expandable microcapsules comprising a
shell of a copolymer produced by polymerizing (I) acrylonitrile, (II) a
carboxyl-group-containing monomer and (III) a monomer containing a group
reactive to the carboxyl group have been disclosed. (Refer to Patent
Reference 3.) The heat-expandable microcapsules have good heat
resistance. On the other hand, the carboxyl group and the group reactive
to the carboxyl group, which are uniformly distributed in the copolymer,
may excessively promote crosslinking when the microcapsules are heated
and expanded. The hollow particulates produced by heating and expanding
the microcapsules have good solvent resistance owing to the promoted
cross-linking in the heating and expanding, while the solvent resistance
is required to be improved to higher grade.

[0005] Patent Reference 4 describes a variant of heat-expandable
microcapsules which comprise a shell of a copolymer having a
polymethacrylimide structure produced from methacrylonitrile and
methacrylic acid and a blowing agent being encapsulated therein. The
heat-expandable microcapsules also have good heat resistance. However,
the shell has poor gas-barrier performance and solvent resistance,
because the high ratio of methacrylonitrile in the copolymer resin
constituting the shell decreases the crystallinity of the copolymer
resin. The poor gas-barrier performance remarkably deteriorates the heat
resistance and expansion performance of the microcapsules employed in
resin molding where the microcapsules are held in a high-temperature
environment for a long time.

[0010] The object of the present invention is to provide heat-expandable
microspheres having high heat and solvent resistance, a process for
producing the same and application thereof.

Technical Solution

[0011] For solving the problems described above, the inventors of the
present invention have studied diligently and have found that the
heat-expandable microspheres described in 1) and/or 2) below solve the
problem mentioned above, and have achieved the present invention.

[0012] 1) heat-expandable microspheres produced by treating the surface of
base-material microspheres with an organic compound containing a metal of
the Groups from 3 to 12 in the Periodic Table, wherein the base-material
microspheres comprise a shell of a thermoplastic resin produced by
polymerizing a polymerizable component including a
carboxyl-group-containing monomer.

[0013] 2) heat-expandable microspheres comprising a shell of a
thermoplastic resin produced by polymerizing a polymerizable component
including a carboxyl-group-containing monomer, and resulting in minimum
ranges of variation (decrease, in most cases) in their
expansion-initiating and maximum expansion temperatures, the variation
being caused by their contact with water.

[0014] Specifically, heat-expandable microspheres of the present invention
comprise a shell of a thermoplastic resin and a thermally vaporizable
blowing agent being encapsulated therein. The thermoplastic resin
comprises a copolymer produced by polymerizing a polymerizable component
including a carboxyl-group-containing monomer, and the surface of the
heat-expandable microspheres is treated with an organic compound
containing a metal of the Groups from 3 to 12 in the Periodic Table.

[0015] The organic compound containing the metal should preferably be a
metal-amino acid compound and/or a compound having at least one bond
represented by the following chemical formula (1):

M-O--C (1)

(where "M" is an atom of a metal of the Groups from 3 to 12 in the
Periodic Table; and the carbon atom, "C", bonds to the oxygen atom, "O",
and also bonds only to a hydrogen atom and/or a carbon atom except the
oxygen atom, "O").

[0016] The organic compound containing the metal should preferably be
soluble in water.

[0017] The amount of the metal should preferably range from 0.05 to 15
weight percent of the heat-expandable microspheres.

[0018] The metal should preferably belong to the Groups 4 and 5 in the
Periodic Table.

[0019] The amount of the carboxyl-group-containing monomer should
preferably be greater than 50 weight percent of the polymerizable
component.

[0020] It is preferable that the polymerizable component further comprises
a nitrile monomer.

[0021] The ranges of the variation in the expansion-initiating temperature
and maximum expansion temperature of the heat-expandable microspheres
after dispersing 5 parts by weight of the microspheres in 100 parts by
weight of deionized water should preferably be not greater than 10
percent of the temperatures before the dispersion.

[0022] An alternative type of the heat-expandable microspheres of the
present invention comprises a shell of a thermoplastic resin and a
thermally vaporizable blowing agent being encapsulated therein, and the
thermoplastic resin comprises a copolymer produced by polymerizing a
polymerizable component including a carboxyl-group-containing monomer.
The maximum expansion ratio of the heat-expandable microspheres is at
least 30 times. The ranges of the variation in the expansion-initiating
temperature and maximum expansion temperature of the heat-expandable
microspheres after dispersing 5 parts by weight of the microspheres in
100 parts by weight of deionized water should preferably be not greater
than 10 percent of the temperatures before the dispersion.

[0023] Those heat-expandable microspheres should preferably meet at least
one of the following requirements (1) to (4).

[0024] (1) The blowing agent comprises a hydrocarbon having a boiling
point at least -20 deg. C. and lower than 170 deg. C. and a hydrocarbon
having a boiling point ranging from 170 deg. C. to 360 deg. C.

[0025] (2) The ratio of DMF-insoluble matter contained in the
heat-expandable microspheres is at least 75 weight percent.

[0026] (3) The maximum expansion temperature and maximum expansion ratio
of the heat-expandable microspheres are at least 240 deg. C. and at least
30 times, respectively.

[0027] (4) The heat-expandable microspheres are wet with a liquid.

[0028] The process for producing the heat-expandable microspheres of the
present invention comprises the step of treating the surface of
base-material microspheres with an organic compound containing a metal of
the Groups from 3 to 12 in the Periodic Table, wherein the base-material
microspheres comprise a shell of a thermoplastic resin produced by
polymerizing a polymerizable component including a
carboxyl-group-containing monomer, and a thermally vaporizable blowing
agent being encapsulated therein.

[0029] The surface treatment should preferably be carried out by mixing
the base-material microspheres and the metal-containing organic compound
in an aqueous dispersion medium.

[0030] Further, the process should preferably comprise, prior to the
surface-treatment step, a step of producing the base-material
microspheres by polymerizing the polymerizable component in an aqueous
dispersion medium in which an oily mixture containing the polymerizable
component and a blowing agent are dispersed. The surface treatment should
preferably be carried out in the liquid after the polymerization in which
the base-material microspheres are contained.

[0031] The surface treatment should preferably be carried out by spraying
a liquid comprising the metal-containing organic compound to the
base-material microspheres.

[0032] Furthermore, the process should preferably comprise a step of
wetting, with a liquid, heat-expandable microspheres produced at the
surface treatment step.

[0033] The hollow particulates of the present invention are produced by
heating and expanding the heat-expandable microspheres mentioned above
and/or the heat-expandable microspheres produced in the process mentioned
above.

[0034] The composition of the present invention contains at least one
particulate material selected from the group consisting of the
heat-expandable microspheres mentioned above, the heat-expandable
microspheres produced in the process mentioned above and the hollow
particulates mentioned above, and a base component.

[0035] The formed product of the present invention is produced by the
method of producing the composition mentioned above.

Advantageous Effects

[0036] The heat-expandable microspheres of the present invention have high
solvent resistance and high heat resistance.

[0037] The process for producing the heat-expandable microspheres of the
present invention can efficiently produce heat-expandable microspheres of
good solvent resistance and good heat resistance.

[0038] The hollow particulates of the present invention, which are
produced from the heat-expandable microspheres, have good solvent
resistance and good heat resistance.

[0039] The compositions of the present invention, which contain the
heat-expandable microspheres and/or hollow particulates, have good
solvent resistance and good heat resistance.

[0040] The formed products of the present invention, which are produced by
the method of producing the compositions mentioned above, are lightweight
and have good solvent resistance.

BRIEF DESCRIPTION OF DRAWINGS

[0041] FIG. 1 is a schematic diagram illustrating an example of
base-material microspheres or heat-expandable microspheres

[0042]FIG. 2 is a graph schematically representing the relation between
the heating temperature and expansion ratio of heat-expandable
microspheres, which have been heated and expanded

[0043]FIG. 3 is a graph representing the temperature for heating the
surface-treated microspheres (5) and the base-material microspheres
without surface treatment (3), and their true specific gravity determined

[0044]FIG. 4 is a graph representing the temperature for heating the
microspheres (5) and the base-material microspheres (3), and their
expansion ratio

[0045]FIG. 5 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (5) and the
base-material microspheres (3), which have been heated and expanded

[0046]FIG. 6 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (6) and (7) and the
base-material microspheres (3), which have been heated and expanded

[0047]FIG. 7 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (8) to (10) and the
base-material microspheres (4), which have been heated and expanded

[0048] FIG. 8 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (11) and the
base-material microspheres (5), which have been heated and expanded

[0049]FIG. 9 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (12) and the
base-material microspheres (6), which have been heated and expanded

[0050] FIG. 10 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (13) and the
base-material microspheres (7), which have been heated and expanded

[0051] FIG. 11 is a graph representing the relation between the heating
temperature and expansion ratio of the microspheres (14) and the
base-material microspheres (8), which have been heated and expanded

[0052]FIG. 12 is a graph comparing the working lives of the microspheres
of Example A1 and Comparative Example A1

[0053] FIG. 13 is a graph schematically representing the relation between
the heating time and weight loss of heat-expandable microspheres, which
have been heated and expanded at the mean temperature of the
expansion-initiating and maximum expansion temperatures

[0054]FIG. 14 is a graph representing the relation between the heating
time and weight loss of the microspheres (9) and the base-material
microspheres (4), which have been heated and expanded at 234 deg. C.

[0055]FIG. 15 is a graph comparing the specific gravities of the formed
products produced in Examples B1 and B2, and in Comparative Examples B1
and B2

BEST MODE FOR CARRYING OUT THE INVENTION

Process for Producing Heat-Expandable Microspheres

[0056] The process for producing the heat-expandable microspheres of the
present invention includes a step of treating the surface of
base-material microspheres with an organic compound containing a metal of
the Groups from 3 to 12 in the Periodic Table (surface treatment step).
The "organic compound containing a metal of the Groups from 3 to 12 in
the Periodic Table" is hereinafter sometimes referred to as "a
metal-containing organic compound".

[0057] Further, the process for producing the heat-expandable microspheres
of the present invention should preferably include a step of producing
the base-material microspheres (base-material microspheres producing
step). In addition, the process for producing the heat-expandable
microspheres of the present invention should preferably include a step in
which heat-expandable microspheres, after the surface-treatment step, are
wetted with liquid (a wetting step).

[0058] The surface treatment step is described below in detail following
to the description of the base-material microspheres and their producing
step, and finally the wetting step is described.

[0059] (Base-Material Microspheres and their Producing Step)

[0060] The base-material microspheres include 1) a shell of a
thermoplastic resin and 2) a thermally vaporizable blowing agent being
encapsulated therein. The thermoplastic resin is produced by polymerizing
a polymerizable component which essentially includes a
carboxyl-group-containing monomer (i.e., a polymerizable component
containing a carboxyl-group-containing monomer).

[0061] At the producing step for base-material microspheres, the
polymerizable component is polymerized in an aqueous dispersion medium in
which an oily mixture including the polymerizable component and a blowing
agent is dispersed.

[0062] The blowing agent is not specifically restricted, except that it is
a thermally vaporizable substance; and includes, for example,
C3-C13 hydrocarbons such as propane, (iso)butane, (iso)pentane,
(iso)hexane, (iso)heptane, (iso)octane, (iso)nonane, (iso)decane,
(iso)undecane, (iso)dodecane and (iso)tridecane; hydrocarbons having a
carbon number greater than 13 and not greater than 20, such as
(iso)hexadecane and (iso)eicosane; hydrocarbons from petroleum fractions
such as pseudocumene, petroleum ether, and normal paraffins and
isoparaffins having an initial boiling point ranging from 150 to 260 deg.
C. and/or being distilled at a temperature ranging from 70 to 360 deg.
C.; their halides; fluorine-containing compounds, such as
hydrofluoroether; tetraalkyl silane; and compounds which thermally
decompose to generate gases. One of or a combination of at least two of
those blowing agents can be employed. The blowing agents can be any of
linear-chain, branched-chain or alicyclic compounds, and should
preferably be aliphatic hydrocarbons.

[0063] The blowing agent is thermally vaporizable. A blowing agent
encapsulated in heat-expandable microspheres should preferably have a
boiling point not higher than the softening point of the thermoplastic
resin shell of the microspheres, because such agent can generate vapor to
a pressure sufficient to expand the heat-expandable microspheres at their
expanding temperature and attain high expansion ratio. In addition,
another blowing agent having a boiling point higher than the softening
point of the thermoplastic resin shell can be encapsulated along with the
blowing agent having a boiling point not higher than the softening point
of the thermoplastic resin shell.

[0064] If a substance having a boiling point higher than the softening
point of the thermoplastic resin shell is encapsulated in microspheres as
a blowing agent, the ratio of such a substance in the whole of the
blowing agent encapsulated in the microspheres is not specifically
restricted, but should preferably be not greater than 95 weight percent,
more preferably not greater than 80 weight percent, further preferably
not greater than 70 weight percent, further more preferably not greater
than 65 weight percent, still further more preferably not greater than 50
weight percent, and most preferably smaller than 30 weight percent. If
the ratio of a substance having a boiling point higher than the softening
point of the thermoplastic resin shell exceeds 95 weight percent of the
whole of a blowing agent encapsulated in microspheres, the expansion
ratio of the microspheres will decrease while their maximum expansion
temperature will increase.

[0065] There is another alternative for the blowing agent, that is, a
blowing agent including a low-boiling-point hydrocarbon (A) and a
high-boiling-point hydrocarbon (B). This alternative agent is preferable
because it enables to increase the expansion-initiating temperature of
heat-expandable microspheres to 220 deg. C. or higher temperature without
decreasing the expanding ratio of the microspheres. One of or both of the
low-boiling point hydrocarbon (A) and high-boiling point hydrocarbon (B)
can be a mixture of hydrocarbons.

[0066] The weight ratio of the low-boiling point hydrocarbon (A) to the
high-boiling point hydrocarbon (B), (A:B), is not specifically
restricted, and should preferably range from 90:10 to 5:95, more
preferably from 80:20 to 10:90, further more preferably from 70:30 to
15:85, and most preferably from 65:35 to 20:80. A weight ratio greater
than 90:10, may fail to attain sufficiently a high expansion-initiating
temperature of the microspheres. A weight ratio smaller than 5:95, may
decrease the expansion ratio of the microspheres.

[0067] The boiling point of the low-boiling point hydrocarbon (A) is
usually at least -20 deg. C. and lower than 170 deg. C., and should
preferably range from 25 to 140 deg. C., more preferably from 50 to 130
deg. C., and most preferably from 55 to 110 deg. C.

[0069] Of those low-boiling-point hydrocarbons (A), hydrocarbons having a
boiling point ranging from 55 to 110 deg. C. (for example, isohexane and
isooctane) are preferable. The ratio of the hydrocarbons having a boiling
point ranging from 55 to 110 deg. C. in the low-boiling point hydrocarbon
(A) is not specifically restricted, but should preferably range from 50
to 100 weight percent, more preferably from 70 to 100 weight percent, and
most preferably from 90 to 100 weight percent. A ratio lower than 50
weight percent may result in insufficiently high expansion-initiating
temperature of microspheres.

[0070] The boiling point of the high-boiling-point hydrocarbon (B) usually
ranges from 170 to 360 deg. C. and should preferably range from 185 to
300 deg. C., more preferably from 200 to 270 deg. C., and most preferably
from 210 to 265 deg. C.

[0072] Of those high-boiling point hydrocarbons (B), hydrocarbons having a
boiling point ranging from 210 to 265 deg. C. (for example,
isohexadecane) are preferable. The ratio of the hydrocarbons having a
boiling point ranging from 210 to 265 deg. C. in the high-boiling point
hydrocarbon (B) is not specifically restricted, but should preferably
range from 50 to 100 weight percent, more preferably from 70 to 100
weight percent, and most preferably from 90 to 100 weight percent. A
ratio lower than 50 weight percent may result in insufficiently high
expansion ratio of microspheres.

[0073] The polymerizable component is polymerized (preferably in the
presence of a polymerization initiator) to form the shell of
heat-expandable microspheres (base-material microspheres). The
polymerizable component essentially includes a monomer component and
optionally contains a cross-linking agent.

[0074] The monomer component usually includes a component referred to as a
(radically) polymerizable monomer having one polymerizable double bond.
The monomer component essentially includes a carboxyl-group-containing
monomer.

[0075] The carboxyl-group-containing monomer is not specifically
restricted, except that it contains at least one free carboxyl group per
one molecule, and the monomer includes unsaturated monocarboxylic acids,
such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid
and cinnamic acid; unsaturated dicarboxylic acids, such as maleic acid,
itaconic acid, fumaric acid, citraconic acid and chloromaleic acid;
anhydrides of unsaturated dicarboxylic acids; and monoesters of
unsaturated dicarboxylic acids, such as monomethyl maleate, monoethyl
maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate,
monomethyl itaconate, monoethyl itaconate and monobutyl itaconate. One of
or a combination of at least two of those carboxyl-group-containing
monomers can be employed. Part or whole of the carboxyl groups contained
in the carboxyl-group-containing monomers can be neutralized in or after
the polymerization. Of those carboxyl-group-containing monomers, acrylic
acid, methacrylic acid, maleic acid, maleic acid anhydride and itaconic
acid are preferable, acrylic acid and methacrylic acid are more
preferable, and methacrylic acid is most preferable for high gas-barrier
performance of resultant microspheres.

[0076] The monomer component essentially includes a
carboxyl-group-containing monomer and can optionally include at least one
of other monomers. Other monomers are not specifically restricted, and
include, for example, nitrile monomers such as acrylonitrile,
methacrylonitrile and fumaronitrile; halogenated vinyl monomers, such as
vinyl chloride; halogenated vinylidene monomers, such as vinylidene
chloride; vinyl ester monomers, such as vinyl acetate, vinyl propionate,
and vinyl butyrate; (meth)acrylic acid ester monomers, such as
methyl(meth)acrylate, ethyl(meth)acrylate, n-butyl(meth)acrylate, t-butyl
(meth)acrylate, 2-ethylhexyl(meth)acrylate, stearyl(meth)acrylate,
phenyl(meth)acrylate, isobornyl(meth)acrylate, cyclohexyl(meth)acrylate,
benzyl(meth)acrylate and 2-hydroxyethyl(meth)acrylate; (meth)acrylamide
monomers, such as acrylamide, substituted acrylamide, methacrylamide and
substituted methacrylamide; maleimide monomers, such as N-phenyl
maleimide and N-cyclohexyl maleimide; styrene monomers, such as styrene
and α-methyl styrene; ethylenically unsaturated monoolefin
monomers, such as ethylene, propylene and isobutylene; vinyl ether
monomers, such as vinyl methyl ether, vinyl ethyl ether and vinyl
isobutyl ether; vinyl ketone monomers, such as vinyl methyl ketone;
N-vinyl monomers, such as N-vinyl carbazole and N-vinyl pyrolidone; and
vinylnaphthalene salts. The term, (meth)acryl, means acryl or methacryl.

[0077] The monomer component should preferably include at least one
monomer selected from the group consisting of nitrile monomers,
(meth)acrylic acid ester monomers, styrene monomers, vinyl ester
monomers, acrylamide monomers and halogenated vinylidene monomers, in
addition to a carboxyl-group-containing monomer.

[0078] The amount of the carboxyl-group-containing monomer in the monomer
component should preferably range from 10 to 90 weight percent, more
preferably from 30 to 90 weight percent, further preferably from 40 to 90
weight percent, further more preferably from above 51.2 weight percent to
90 weight percent, and most preferably from 53 to 90 weight percent, in
order to upgrade the heat resistance and solvent resistance of the
resultant heat-expandable microspheres and extending their working
temperature range and working life. An amount of the
carboxyl-group-containing monomer lower than 10 weight percent may fail
to attain sufficient heat resistance of resultant microspheres and
consequently fail to attain stable expansion performance of resultant
microspheres in high temperature range over a long time. An amount of the
carboxyl-group-containing monomer higher than 90 weight percent may
degrade the expansion performance of microspheres.

[0079] A monomer component further including a nitrile monomer is
preferable for improving the gas-barrier performance of the thermoplastic
resin shell of microspheres.

[0080] In a monomer component essentially including a nitrile monomer, the
ratio of the mixture of a carboxyl-group-containing monomer and nitrile
monomer in the monomer component should preferably be at least 50 weight
percent, more preferably at least 60 weight percent, further preferably
at least 70 weight percent, further more preferably at least 80 weight
percent, and most preferably at least 90 weight percent.

[0081] In this case, the ratio of the carboxyl-group-containing monomer in
the mixture of the carboxyl-group-containing monomer and nitrile monomer
should preferably range from 10 to 90 weight percent, more preferably
from 30 to 90 weight percent, further preferably from 40 to 90 weight
percent, further more preferably from above 51.2 weight percent to 90
weight percent, and most preferably from 53 to 90 weight percent. An
amount of the carboxyl-group-containing monomer lower than 10 weight
percent may fail to impart sufficient heat resistance and solvent
resistance to resultant microspheres and consequently fail to attain
stable expansion performance of the resultant heat-expandable
microspheres in high temperature range over a long time. An amount of the
carboxyl-group-containing monomer higher than 90 weight percent may
degrade the expansion performance of resultant heat-expandable
microspheres.

[0083] The ratio of at least one monomer selected from the group
consisting of vinylidene chloride, (meth)acrylic acid ester monomer,
(meth)acrylamide monomer and styrene monomer in the monomer component
should preferably be less than 50 weight percent, more preferably less
than 30 weight percent, and most preferably less than 10 weight percent.
If the ratio of the monomer is equal to or greater than 50 weight
percent, the heat resistance of resultant microspheres may be degraded.

[0084] The monomer component can include a monomer reactive to the
carboxyl group in a carboxyl-group-containing monomer. A monomer
component including a monomer reactive to the carboxyl group further
upgrades the heat resistance of the resultant microspheres and improves
their expansion performance at high temperature. The monomers reactive to
the carboxyl group include, for example, N-methylol (meth)acrylamide,
N,N-dimethylaminoethyl(meth)acrylate,
N,N-dimethylaminopropyl(meth)acrylate, vinyl glycidyl ether, propenyl
glycidyl ether, glycidyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate,
2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and
2-hydroxy-3-phenoxypropyl(meth)acrylate. The ratio of the monomer
reactive to the carboxyl group should preferably range from 0.1 to 10
weight percent, and more preferably from 3 to 5 weight percent of the
monomer component.

[0085] The polymerizable component can include, in addition to the
monomers mentioned above, a polymerizable monomer (cross-linking agent)
having at least two polymerizable double bonds. A shell of a
thermoplastic resin polymerized with a cross-linking agent minimizes the
loss in the retention (retention in microspheres) of a blowing agent in
thermally expanded microspheres so as to achieve sufficient thermal
expansion of the microspheres.

[0086] The cross-linking agent is not specifically restricted, and
includes, for example, aromatic divinyl compounds, such as divinyl
benzene; and di(meth)acrylate compounds, such as allyl methacrylate,
triacrylformal, triallyl isocyanate, ethylene glycol di(meth)acrylate,
diethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate,
1,9-nonanediol di(meth)acrylate, PEG (200) di(meth)acrylate, PEG (600)
di(meth)acrylate, trimethylolpropane trimethacrylate, pentaerythritol
tri(meth)acrylate, dipentaerythritol hexaacrylate, and
2-butyl-2-ethyl-1,3-propanediol diacrylate. One of or a combination of at
least two of those cross-linking agents can be used.

[0087] The amount of the cross-linking agent is not specifically
restricted but should preferably range from 0.01 to 5 parts by weight,
more preferably from 0.1 to 1 parts by weight, and most preferably from
over 0.2 to less than 1 parts by weight to 100 parts by weight of a
monomer component. The amount may be less than 0.1 parts by weight to 100
parts by weight of a monomer component, because a highly cross-linked
resin layer can be formed at the outermost layer of resultant
heat-expandable microspheres through the treatment on the external
surface of base-material microspheres at the surface-treatment step
mentioned below. The highly cross-linked resin layer provides the
microspheres of gas-barrier performance, which prevents a blowing agent
from permeating through the thermoplastic resin shell to go out of the
microspheres when the blowing agent is heated and evaporated.
Consequently, heat-expandable microspheres produced with a cross-linking
agent in an amount less than 0.1 parts by weight still retains good
expansion performance.

[0088] The amount of the carboxyl-group-containing monomer in the
polymerizable component should preferably be at least 10 weight percent,
more preferably at least 30 weight percent, further preferably at least
40 weight percent, further more preferably greater than 50 weight
percent, and most preferably at least 53 weight percent, for the purpose
of upgrading the heat resistance and solvent resistance of the resultant
heat-expandable microspheres and extending their working temperature
range and working life. An amount of the carboxyl-group-containing
monomer less than 10 weight percent may fail to attain sufficient heat
resistance and solvent resistance of resultant microspheres and
consequently fail to attain stable expansion performance of the resultant
microspheres in high temperature range over a long time. An amount of the
carboxyl-group-containing monomer higher than 90 weight percent may
degrade the expansion performance of resultant microspheres.

[0089] At the producing step for base-material microspheres, it is
preferable to employ an oily mixture containing a polymerization
initiator to polymerize the polymerizable component in the presence of
the polymerization initiator.

[0090] The polymerization initiator is not specifically restricted, and
includes, for example, peroxides and azo compounds.

[0092] The azo compounds include, for example,
2,2'-azobis(4-methoxy-2,4-dimethyl valeronitrile), 2,2'-azobis
isobutylonitrile, 2,2'-azobis(2,4-dimethyl valeronitrile),
2,2'-azobis(2-methyl propionate) and 2,2'-azobis(2-methyl butyronitrile).
One of or a combination of at least two of the polymerization initiators
can be employed. The polymerization initiator should preferably be an
oil-soluble polymerization initiator which is soluble in the monomer
component. Of those polymerization initiators mentioned above,
peroxydicarbonates are preferable. In a polymerization initiator
including a peroxidicarbonate and other polymerization initiators, the
peroxidicarbonate should preferably e constitute at least 60 weight
percent.

[0093] The amount of the polymerization initiator in the monomer component
is not specifically restricted but should preferably range from 0.3 to
8.0 parts by weight to 100 parts by weight of the monomer component.

[0094] At the producing step of the base-material microspheres, the oily
mixture can further include a chain transfer agent.

[0095] The aqueous dispersion medium mainly includes water, such as
deionized water, for dispersing an oily mixture, and can further include
alcohols such as methanol, ethanol and propanol, and hydrophilic organic
solvents such as acetone. In the present invention, the term,
"hydrophilic", refers to a state of a chemical being miscible in water to
a prescribed amount. The amount of the aqueous dispersion medium is not
specifically restricted, but should preferably range from 100 to 1,000
parts by weight to 100 parts by weight of a polymerizable component.

[0096] The aqueous dispersion medium can further include an electrolyte,
such as sodium chloride, magnesium chloride, sodium sulfate, magnesium
sulfate, ammonium sulfate and sodium carbonate. One of or a combination
of at least two of those electrolytes can be employed. The amount of the
electrolyte is not specifically restricted but should preferably range
from 0.1 to 50 parts by weight to 100 parts by weight of the aqueous
dispersion medium.

[0097] The aqueous dispersion medium can include at least one
water-soluble compound selected from the group consisting of
water-soluble 1,1-substituted compounds having a structure in which a
hetero atom and a hydrophilic functional group selected from the group
consisting of hydroxyl group, carboxylic acid (salt) groups and
phosphonic acid (salt) groups are bonded to the same carbon atom;
potassium dichromate; alkali metal nitrites; metal (trivalent) halides;
boric acid; water-soluble ascorbic acids; water-soluble polyphenols;
water-soluble vitamin Bs; and water-soluble phosphonic acids (salts). In
the present invention, the term, "water-soluble" means that at least 1 g
of a substance is soluble in 100 g of water.

[0098] The amount of the water-soluble compound in the aqueous dispersion
medium is not specifically restricted but should preferably range from
0.0001 to 1.0 parts by weight, more preferably from 0.0003 to 0.1 parts
by weight, and most preferably from 0.001 to 0.05 parts by weight to 100
parts by weight of a polymerizable component. An insufficient amount of
the water-soluble compound may fail to attain the effect by the
water-soluble compound. On the other hand, an excessive amount of the
water-soluble compound may decrease polymerization rate or increase the
amount of polymerizable component which remains unpolymerized after
polymerization.

[0099] The aqueous dispersion medium can include a dispersion stabilizer
or dispersion-stabilizing auxiliary in addition to the electrolyte and
water-soluble compound.

[0100] The dispersion stabilizer is not specifically restricted, and
include, for example, tribasic calcium phosphate; pyrophosphates produced
by metathesis reaction such as magnesium pyrophosphate and calcium
pyrophosphate; colloidal silica; and alumina sol. One of or a combination
of those dispersion stabilizers can be employed.

[0101] The amount of the dispersion stabilizer should preferably range
from 0.1 to 20 parts by weight, and more preferably from 0.5 to 10 parts
by weight to 100 parts by weight of a polymerizable component.

[0102] The dispersion-stabilizing auxiliary is not specifically
restricted, and includes, for example, polymer-type
dispersion-stabilizing auxiliaries; and surfactants, such as cationic
surfactants, anionic surfactants, amphoteric surfactants and nonionic
surfactants. One of or a combination of at least two of those
dispersion-stabilizing auxiliaries can be employed.

[0103] The aqueous dispersion medium is prepared, for example, by blending
the water-soluble compound and optionally a dispersion stabilizer and/or
dispersion stabilizing auxiliary in water (deionized water). The pH of
the aqueous dispersion medium in polymerization is determined according
to the variants of the water-soluble compound, dispersion stabilizer and
dispersion stabilizing auxiliary.

[0104] At the producing step of base-material microspheres, the
polymerization can be carried out in the presence of sodium hydroxide or
the presence of sodium hydroxide and zinc chloride.

[0105] At the producing step for base-material microspheres, an oily
mixture is dispersed and emulsified in an aqueous dispersion medium to
form oil globules of prescribed diameter.

[0106] The methods for dispersing and emulsifying the oily mixture include
generally known dispersion techniques, such as agitation with a
Homo-mixer (for example, those produced by Tokushu Kika Kogyou),
dispersion with a static dispersing apparatus such as a Static mixer (for
example, those produced by Noritake Engineering Co., Ltd.), membrane
emulsification technique, and ultrasonic dispersion.

[0107] Then suspension polymerization is initiated by heating the
dispersion in which the oily mixture is dispersed into oil globules in
the aqueous dispersion medium. During the polymerization reaction, it is
preferable to gently agitate the dispersion to a degree which prevents
the floating of monomers and sedimentation of polymerized heat-expandable
microspheres.

[0108] The polymerization temperature can be freely settled according to
the variant of a polymerization initiator, and should preferably be
controlled within the range from 30 to 100 deg. C., and more preferably
from 40 to 90 deg. C. The polymerization temperature should preferably be
maintained for about 0.1 to 20 hours. The initial pressure for the
polymerization is not specifically restricted, but should preferably be
controlled within the range from 0 to 5.0 MPa, more preferably from 0.1
to 3.0 MPa in gauge pressure.

[0109] The base-material microspheres should preferably be produced
without the presence of the metal-containing organic compounds which are
described below in detail.

[0110] Although the base-material microspheres should preferably be
produced at the step of producing base-material microspheres mentioned
above, the producing technique is not specifically restricted.

[0111] The base-material microspheres have an average particle size and
coefficient of variation (CV) in particle size distribution which are in
similar ranges to those of heat-expandable microspheres mentioned below.
However, the true specific gravity, retention ratio of an encapsulated
blowing agent, working temperature range, working life, maximum expansion
temperature and ratio of DMF-insoluble matter of the base-material
microspheres before the surface treatment are sometimes different from
those of heat-expandable microspheres after the surface treatment, as
mentioned below. Especially, the working temperature range, working life,
maximum expansion temperature and ratio of DMF-insoluble matter of the
base-material microspheres can be greatly different from those of the
heat-expandable microspheres.

[0112] (Surface Treatment Step)

[0113] At the surface treatment step, the surface of base-material
microspheres is treated with a metal-containing organic compound. The
metal-containing organic compound is not specifically restricted, but
should preferably be water-soluble for high surface treatment efficiency.

[0117] The valence of the metals mentioned above is not specifically
restricted, and should preferably range from 2 to 5, more preferably from
3 to 5, and most preferably from 4 to 5, for the cross-linking efficiency
per one metal atom. A metal atom having a valence of 1 may deteriorate
the solvent resistance and water resistance of resultant heat-expandable
microspheres while a metal atom having a valence of 6 or more may
decrease the cross-linking efficiency.

[0118] Metals and their valence preferable for constituting the
metal-containing organic compound are zinc (valence of 2), cadmium
(valence of 2), aluminium (valence of 3), vanadium (valence of 3),
ytterbium (valence of 3), titanium (valence of 4), zirconium (valence of
4), lead (valence of 4), cerium (valence of 4), vanadium (valence of 5),
niobium (valence of 5) and tantalum (valence of 5) because of improved
heat resistance of resultant microspheres.

[0119] The metal-containing organic compound should preferably be a
metal-amino acid compound and/or a compound having at least one bond
represented by the following chemical formula (1);

M-O--C (1)

(where "M" is an atom of a metal of the Groups from 3 to 12 in the
Periodic Table; and the carbon atom, "C", bonds to the oxygen atom, "O",
and also bonds only to a hydrogen atom and/or carbon atom other than the
oxygen atom "O").

[0120] At first, the compound having at least one bond represented by the
chemical formula (1) is described in detail.

[0121] The compound having at least one bond represented by the chemical
formula (1)

[0122] The bond between a metal atom and oxygen atom (M-O bond)
illustrated in the chemical formula (1) can be either an ionic bond or
covalent bond (including a coordinate bond), and a covalent bond is
preferable.

[0123] If the compound having at least one bond represented by the
chemical formula (1) has a metal-alkoxide bond and/or metal-aryloxide
bond, the compound can impart good solvent resistance and expansion
performance which is stable in a high and broad temperature range to the
resultant heat-expandable microspheres. Hereinafter, the "metal-alkoxide
bond and/or metal-aryloxide bond" is sometimes referred to as "MO bond"
and the "compound having a metal-alkoxide bond and/or metal-aryloxide
bond" is sometimes referred to as "MO compound" for simplifying the
description.

[0124] The MO compound contains at least one metal-alkoxide bond or
metal-aryloxide bond. The MO compound can further contain a metallic bond
other than the MO bond, such as metal-O--C═O bond (metal-acylate
bond), metal-OCON bond (metal-carbamate bond), metal=O bond (metal-oxy
bond) and metal-acetyl-acetonate bond represented by the chemical formula
(2) (where each R1 and R2 is an organic group and can be the same or
different) shown below. The symbol, M, represents a metal.

##STR00001##

[0125] As clearly mentioned above, the MO bond and metal-O--C═O bond
(metal-acylate bond) are different, and the metal-O--C═O bond does
not contain the MO bond.

[0126] The MO compounds can be classified into four groups of compounds,
Compounds (1) to (4), described below.

[0127] Compound (1):

[0128] The compound (1) includes a metal alkoxide and metal aryloxide
represented by the following chemical formula (A).

M(OR)n (A)

(where "M" represents a metal; "n" is the valence of the metal; "R" is a
C1 to C20 hydrocarbon group; and each of the hydrocarbon groups
existing in the number of "n" can be the same or different, and can be
linear-chain, branched-chain or alicyclic group)

[0129] The "M" (metal) and "n" (valence) in the compound (1) are those
mentioned above.

[0131] The compound (1) include, for example, zinc (valence of 2)
alkoxides, such as zinc diethoxide and zinc diisopropoxide; cadmium
(valence of 2) alkoxides such as cadmium dimethoxide and cadmium
diethoxide; aluminium (valence of 3) alkoxides, such as aluminium
triisopropoxide and aluminium triethoxide; vanadium (valence of 3)
alkoxides, such as vanadium triethoxide and vanadium triisopropoxide;
ytterbium (valence of 3) alkoxides, such as ytterbium triethoxide and
ytterbium triisopropoxide; titanium (valence of 4) alkoxides, such as
tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium,
tetranormalpropoxytitanium, tetranormalbutoxytitanium,
tetrakis(2-ethylhexyloxy) titanium, and tetraphenoxytitaium; zirconium
(valence of 4) alkoxides, such as tetramethoxyzirconium,
tetraethoxyzirconium, tetraisopropoxyzirconium,
tetranormalpropoxyzirconium, tetranormalbutoxyzirconium,
tetrakis(2-ethylhexyloxy)zirconium, and zirconium tetraphenolate; lead
(valence of 4) alkoxides, such as tetranormalpropoxylead and
tetranormalbutoxylead; cerium (valence of 4) alkoxides, such as
tetramethoxycerium, tetraethoxycerium, tetraisopropoxycerium,
tetranormalpropoxycerium, tetranormalbutoxycerium,
tetrakis(2-ethylhexyloxy)cerium, and cerium tetraphenolate; niobium
(valence of 5) alkoxide, such as niobium pentamethoxide, niobium
pentaethoxide and niobium pentabutoxide; vanadium (valence of 5)
alkoxyoxides, such as trimethoxioxyvanadium, triethoxioxyvanadium,
tri(n-propoxy)oxyvanadium, isopropoxioxyvanadium,
tri(n-butoxide)oxyvanadium, and isobutoxioxyvanadium; and other metal
alkoxides, such as the alkoxides of tantalum, manganese, cobalt and
copper.

[0132] Compound (2)

[0133] The compound (2) includes the oligomer and polymer of the compound
(1) mentioned above, and is usually produced in the condensation reaction
with the compound (1). The compound (2) is represented by the chemical
formula (B) shown below. The chemical formula (B) represents a partially
hydrolyzed compound.

RO[-M(OR)2O--]x-1R (B)

(where "M" and "R" represent the same as those in the chemical formula
(A); and "x" is an integer at least 2)

[0134] The molecular weight of the compound (2) is not specifically
restricted, but the number average molecular weight of the compound
should preferably range from 200 to 5000, and more preferably from 300 to
3000. A compound having a number average molecular weight less than 200
may result in poor cross-linking efficiency, and a compound having a
number average molecular weight greater than 5000 may result in difficult
control of the degree of cross-linking.

[0135] The compound (2) include, for example, a titanium alkoxide polymer
or titanium alkoxide dimer being represented by the chemical formula (B)
where "x" ranges from 2 to 15.

[0138] The compound (3) is a metal chelate compound containing the MO
bond. The compound (3) is a metal chelate compound containing at least
one MO bond in which a ligand moiety containing at least one
electron-releasing group selected from the group consisting of hydroxyl
group, keto group, carboxyl group and amino group is coordinated to the
M. The ligand moiety contains at least one electron-releasing group, and
preferably two to four electron-releasing groups. The compound (3) can
contain a plurality of the MO bonds, M, and ligand moieties.

[0158] The metal-containing organic compound may be a metal-amino acid
compound. The metal-amino acid compound can be produced in the reaction
of a salt of a metal of the Groups from 3 to 12 in the Periodic Table and
an amino acid described below.

[0159] The amino acid includes not only amino acids containing an amino
group (--NH2) and carboxyl group (--COOH) in the same molecule, but
also imino acids such as proline and hydroxy proline, in which an imino
group is contained instead of an amino group. The amino acid is usually
α-amino acid, and can be β-, γ-, δ- or
ω-amino acid.

[0160] The amino acid includes amino acids which are produced by
substituting one or two hydrogen atoms of an amino group contained in an
amino acid, and amino acid derivatives which are chelate compounds
produced by chelating the nitrogen atom of an amino group and the oxygen
atom of a carboxyl group contained in an amino acid.

[0163] The preferable salt of a metal of the Groups from 3 to 12 in the
Periodic Table to be reacted with the amino acids mentioned above is a
basic zirconyl chloride. An example of commercially available metal-amino
acid compounds is ORGATIX ZB-126 (produced by Matsumoto Seiyaku Kogyo
Co., Ltd.).

[0165] The molar ratio of the metal-containing organic compound (the mole
number of the metal-containing organic compound to the mole number of the
carboxyl group-containing monomer which is the raw material of a
base-material microsphere) for the surface treatment is not specifically
restricted, but should preferably range from 0.001 to 1.0, more
preferably from 0.005 to 0.5, further preferably from 0.007 to 0.3,
further more preferably from 0.009 to 0.15, and most preferably from
0.009 to 0.06. A molar ratio of the metal-containing organic compound
less than 0.001 may fail to sufficiently upgrade the heat resistance of
resultant microspheres and may decrease the expansion performance of the
microspheres being held at high temperature for a long time. On the other
hand, a molar ratio of the metal-containing organic compound greater than
1.0 may make excessively hard shell of resultant heat-expandable
microspheres to decrease their expansion performance.

[0166] The surface treatment step is not specifically restricted, except
that a metal-containing organic compound is brought into contact with
base-material microspheres at the step, and the surface treatment should
preferably be carried out by mixing base-material microspheres and a
metal-containing organic compound with the aqueous dispersion medium
mentioned above. Thus, the metal-containing organic compound should
preferably be soluble in water.

[0167] For carrying out the surface treatment in an aqueous dispersion
medium, the amount of base-material microspheres should preferably range
from 1 to 50 weight percent, more preferably from 3 to 40 weight percent,
and further preferably from 5 to 35 weight percent to a dispersion
mixture including the base-material microspheres, a metal-containing
organic compound and an aqueous dispersion medium. An amount of the
base-material microspheres less than 1 weight percent may degrade the
surface treatment efficiency, while an amount over 50 weight percent may
cause uneven surface treatment.

[0168] The amount of the metal-containing organic compound in the
dispersion mixture is not specifically restricted, so far as that the
surface of the base-material microspheres can be evenly treated, and
should preferably range from 0.1 to 20 weight percent, and more
preferably from 0.5 to 15 weight percent. An amount of the
metal-containing organic compound less than 0.1 weight percent may
degrade the surface treatment efficiency, while an amount over 20 weight
percent may cause uneven surface treatment.

[0170] At the surface treatment step, heat-expandable microspheres can be
produced in the liquid containing the base-material microspheres which
were produced at the step of producing the base-material microspheres.
Or, heat-expandable microspheres can be produced by treating the surface
of base-material microspheres, which have been separated from the liquid
after producing the base-material microspheres, by means of filtration,
washing with water and optionally drying.

[0171] If the aqueous dispersion medium contains other components, the
surface of base-material microspheres can be treated with the methods
from A) to D) described below.

[0172] A) Mixing a component (1) including base-material microspheres and
other components, and a component (2) including a metal-containing
organic compound

[0173] B) Mixing a component (1) including a metal-containing organic
compound and base-material microspheres, and a component (2) including
other components

[0174] C) Mixing a component (1) including a metal-containing organic
compound and other components, and a component (2) including
base-material microspheres

[0175] D) Simultaneously mixing a component (1) including base-material
microspheres, a component (2) including other components, and a component
(3) including a metal-containing organic compound

(where at least one of the components 1 to 3 mentioned above contains
water, and two or three of the components can contain water).

[0176] The surface treatment can be carried out with a technique other
than those mentioned above, for example, with the techniques 1) and 2)
described below.

[0177] 1) Surface Treatment for Wet Base-Material Microspheres
(Base-Material Microspheres in a State of Wet Cake)

[0178] Heat-expandable microspheres are produced by preparing a mixture
including base-material microspheres, a metal-containing organic compound
and an aqueous dispersion medium (in a uniform state), in which the
base-material microspheres should preferably constitute at least 50
weight percent, more preferably at least 60 weight percent and further
more preferably at least 70 weight percent of the mixture, and by
removing the aqueous dispersion medium from the mixture through flash
drying or reduced-pressure thermal drying.

[0180] Heat-expandable microspheres are produced by adding a
metal-containing organic compound to dry base-material microspheres which
includes base-material microspheres and an aqueous dispersion medium (in
a uniform state) and in which the base-material microspheres should
preferably constitute at least 90 weight percent and more preferably at
least 95 weight percent of the dry base-material microspheres, then
mixing uniformly, and by heating the mixture in order to remove volatiles
but not to expand the microspheres. The base-material microspheres can be
heated statically, with agitation, or in a fluidized state in the air by
means of fluidized bed. The metal-containing organic compound should
preferably be added to the dry base-material microspheres by spraying the
compound or a liquid containing the compound uniformly onto the
microspheres.

[0181] The surface-treatment temperature is not specifically restricted,
but should preferably range from 30 to 180 deg. C., more preferably from
40 to 150 deg. C., and most preferably from 50 to 120 deg. C. The
temperature should preferably be maintained for a period ranging from 0.1
to 20 hours.

[0182] The pressure for the surface treatment is not specifically
restricted, but should preferably range from 0 to 5.0 MPa, more
preferably from 0.1 to 3.0 MPa, and further more preferably from 0.2 to
2.0 MPa in gauge pressure.

[0183] At the surface treatment step, heat-expandable microspheres after
the surface treatment are usually separated from the aqueous dispersion
medium through suction filtration, centrifugal separation or centrifugal
filtration. The wet cake of the heat-expandable microspheres after the
separation can be processed into dry heat-expandable microspheres through
flash drying or thermal drying under reduced pressure. Some of these
operations can be omitted optionally in the surface treatment carried out
with the technique 1) or 2) mentioned above.

[0184] After the surface treatment, the amount of the metal of the Groups
from 3 to 12 in the Periodic Table increases in the heat-expandable
microspheres. The increase in the amount of the metal of the Groups from
3 to 12 in the Periodic Table which is contained in the surface-treated
heat-expandable microspheres is usually at least 10 weight percent, and
should preferably be at least 60 weight percent, more preferably at least
70 weight percent, further preferably at least 80 weight percent, further
more preferably at least 90 weight percent and most preferably at least
95 weight percent of the whole amount of the metal of the Groups from 3
to 12 in the Periodic Table which is contained in the surface-treated
heat-expandable microspheres. An increase in the amount less than 10
weight percent makes the shell of the heat-expandable microspheres rigid
and may result in poor expansion performance of the microspheres.

[0185] (Wetting Step)

[0186] Heat-expandable microspheres after the surface treatment are wet
with a liquid at the wetting step. The wetting improves the workability
of a heat-expandable microspheres to improve the dispersibility of the
heat-expandable microspheres in mixing operation for various end uses.

[0187] The liquid employed in the wetting is not specifically restricted,
but should preferably meet the requirements, i.e., having a higher
boiling point than that of the blowing agent encapsulated in
heat-expandable microspheres and not dissolving nor swelling the
thermoplastic resin shell of heat-expandable microspheres.

[0188] The boiling point of the liquid employed at the wetting step should
preferably range from 80 to 270 deg. C., more preferably from 90 to 260
deg. C., and most preferably from 100 to 250 deg. C.

[0189] The liquid employed at the wetting step is not specifically
restricted, and includes, for example, plasticizers such as dibutyl
phthalate, diisooctyl phthalate, dioctyl adipate, tricresyl phosphate,
triethyl citrate, acetyl tributyl citrate, and octyl alcohol which are
used to apply the microspheres obtained by the wetting for the
manufacture of plastics, elastomers, sealants, and paints; and monomers
such as dicyclopentadiene and styrene which are used to apply the
microspheres obtained by the wetting for the manufacture of light-weight
foamed and molded products or adhesives.

[0190] The employable liquids other than those mentioned above include
water, nonionic surfactants, alkylene glycol, polyalkylene glycol,
glycerin, silicone oils, liquid paraffins, process oils, and other oils.
A combination of at least two of those liquids can be employed.

[0191] The amount of a liquid contained in heat-expandable microspheres
which have been wet with the liquid at the wetting step is not
specifically restricted, and determined according to the dust generation
from or the workability of the heat-expandable microspheres.

[0192] The wetting is carried out by shaking and/or agitating
heat-expandable microspheres and a liquid with an ordinary powder mixer
or a mixer equipped with a counter shaft.

[0193] [Heat-Expandable Microspheres and their Application]

[0194] The heat-expandable microspheres of the present invention includes,
as shown in FIG. 1, a shell (1) of a thermoplastic resin, and a thermally
vaporizable blowing agent (2) being encapsulated therein. The
heat-expandable microspheres of the present invention have a similar
structure and appearance as those of the base-material microspheres
mentioned above, though they sometimes have greatly different properties.

[0195] The thermoplastic resin constituting the shell of the
heat-expandable microspheres of the present invention includes a
copolymer produced by polymerizing a polymerizable component which
contains a monomer component essentially including a
carboxyl-group-containing monomer.

[0196] The heat-expandable microspheres of the present invention can be
produced in a process including the surface treatment step mentioned
above, though the process for producing the heat-expandable microspheres
is not restricted within the scope of the process. The description about
the heat-expandable microspheres and its application, which are contained
in the explanation of the process mentioned above, may be hereinafter
sometimes omitted to avoid redundancy. In this case, the explanation of
the process mentioned above should be applied.

[0197] The amount of the metal of the Groups from 3 to 12 in the Periodic
Table which is contained in the heat-expandable microspheres should
preferably range from 0.05 to 15 weight percent of the heat-expandable
microspheres, more preferably from 0.10 to 7 weight percent, further
preferably from 0.13 to 5 weight percent, still further preferably from
0.14 to 3 weight percent, further more preferably from 0.15 to 1.5 weight
percent, still further more preferably from 0.16 to 0.8 weight percent,
and most preferably from 0.20 to 0.54 weight percent. If the amount of
the metal of the Groups from 3 to 12 in the Periodic Table which is
contained in the heat-expandable microspheres is lower than 0.05 weight
percent, the resultant microspheres may have insufficient heat
resistance. On the other hand, if the amount of the metal of the Groups
from 3 to 12 in the Periodic Table which is contained in the
heat-expandable microspheres is greater than 15 weight percent, the
resultant microspheres may have rigid shell and low expansion ratio.
Among the metals of the Groups from 3 to 12 in the Periodic Table,
transition metals are preferable, and metals of the Groups 4 and 5 in the
Periodic Table are more preferable. The detailed description of the
metals contained in heat-expandable microspheres is the same as that for
the metals constituting the metal-containing organic compounds.

[0198] The heat-expandable microspheres of the present invention should
preferably contain high ratio of DMF-insoluble matter. The ratio of
DMF-insoluble matter in the present invention is defined to be the
percent of heat-expandable microspheres which remain after being shaken
in DMF (N,N-dimethyl formamide) without being dissolved in it. (Refer to
the Examples.) High ratio of DMF-insoluble matter implies that the
thermoplastic resin shell of microspheres has dense structure owing to
the cross-linking by a cross-linking agent and/or metal-containing
organic compound, and has high solvent resistance. Heat-expandable
microspheres containing high ratio of DMF-insoluble matter can minimize
the migration of the encapsulated blowing agent through their shells,
which become thin in thermal expansion, and retain good expansion
performance.

[0199] The preferable ranges of the ratio of DMF-insoluble matter are
those described below from 1) to 6) where a latter range is more
preferable than a former and the maximum of the amount is 100 weight
percent. A ratio of DMF-insoluble matter smaller than 75 percent result
in insufficient retention of a blowing agent in microspheres and may
deteriorate the expansion performance of the microspheres being subjected
to high temperature for a long time.

[0201] Some of conventional heat-expandable microspheres containing high
ratio of DMF-insoluble matter include a thermoplastic resin shell having
a dense structure throughout from its outermost to innermost layers. Such
microspheres sometimes have low expansion ratio and fail to meet required
expansion performance (refer to Comparative examples 2 and 3 described
below). On the other hand, the heat-expandable microspheres of the
present invention have a thermoplastic resin shell which is estimated to
be densely cross-linked at its outermost layer to retain its softness,
and thus the microspheres contain high ratio of DMF-insoluble matter.
Owing to such shell, the microspheres retain their encapsulated blowing
agent well and prevent the migration of the blowing agent out of them.
Such microspheres can exhibit high expansion ratio especially in high
temperature region.

[0202] A polyurethane composition including polyurethane and conventional
heat-expandable microspheres dispersed in DMF remarkably loses its
expansion performance with time. Such time-dependent decrease in the
expansion performance of the composition will be greatly restrained, if
the heat-expandable microspheres of the present invention, which have
high solvent resistance, is employed instead of conventional
heat-expandable microspheres.

[0203] If 5 parts by weight of the heat-expandable microspheres of the
present invention are dispersed in 100 parts by weight of deionized
water, the ranges of variation in the expansion-initiating temperature
(ΔTs) and maximum expansion temperature (ΔTmax) of the
microspheres after the dispersion should preferably be not greater than
10 percent, more preferably not greater than 8 percent, further
preferably not greater than 5 percent, and most preferably not greater
than 3 percent. The measuring methods for ΔTs and ΔTmax are
described below in detail. In the measuring, the lower limits of
ΔTs and ΔTmax sometimes reach to about -5 percent, which is
estimated to be caused by error of measurement, but the lower limits are
normally 0 percent.

[0204] In the present invention, the inventors have found that
heat-expandable microspheres which include a shell of a thermoplastic
resin including a copolymer produced from a carboxyl-group-containing
monomer and result in a ΔTs and ΔTmax not greater than 10
percent have high solvent resistance. If one of or both of ΔTs and
ΔTmax of heat-expandable microspheres are greater than 10 percent,
the microspheres have poor solvent resistance.

[0205] Usually, heat-expandable microspheres produced from a
carboxyl-group-containing monomer are highly hydrophilic. Therefore water
penetrates into the thermoplastic resin constituting the shell of the
microspheres dispersed in water, leading to the change (decrease in most
cases) in their basic properties, such as the expansion initiating
temperature and maximum expansion temperature. On the other hand, small
ΔTs and ΔTmax of heat-expandable microspheres indicate that
water hardly penetrates into the thermoplastic resin shell of the
microspheres. This implies that dense polymer structure has been formed
at least on and near the outer surface of the thermoplastic resin shell,
and the structure is estimated to achieve high solvent resistance of the
microspheres.

[0206] On the contrary, hydrophobic heat-expandable microspheres, which
are not produced from hydrophilic monomers such as a
carboxyl-group-containing monomer, do not allow water to penetrate into
the shell including thermoplastic resin when such microspheres are
dispersed in water. The ΔTs and ΔTmax of such microspheres do
not vary usually, and cannot indicate the solvent resistance of the
microspheres.

[0207] In the case that either or both of ΔTs and ΔTmax of
heat-expandable microspheres are greater than 10 percent, the
heat-expandable microspheres have poor solvent resistance as explained
above. In addition, the expansion performance of such heat-expandable
microspheres deteriorates after they are dispersed in water, and their
stability in processing in an aqueous medium may be adversely affected.
Especially, in a wet processing of heat-expandable microspheres with
water, alkaline metals inonically bonded to the carboxyl group in the
thermoplastic resin shell of the heat-expandable microspheres leads to
increase in the ΔTmax of the microspheres and remarkably decrease
the maximum expansion temperature of the microspheres.

[0208] The average particle size of the heat-expandable microspheres is
not specifically restricted, but should preferably range from 1 to 100
μm, more preferably from 2 to 80 μm, further preferably from 3 to
60 μm, and most preferably from 5 to 50 μm.

[0209] The coefficient of variation, CV, in the particle size distribution
of heat-expandable microspheres is not specifically restricted, but
should preferably be not greater than 35 percent, more preferably not
greater than 30 percent, and further preferably not greater than 25
percent. The coefficient of variation, CV, can be calculated by the
expressions (1) and (2) shown below.

(where "s" represents a standard deviation of the particle size of
microspheres, <x> represents an average particle size, "xi"
represents the particle size of i-th particle, and "n" represents the
number of particles)

[0210] The retention ratio of a blowing agent encapsulated in
heat-expandable microspheres is not specifically restricted, but should
preferably range from 2 to 60 weight percent, more preferably from 5 to
50 weight percent, further preferably from 8 to 45 weight percent, and
further more preferably from 10 to 40 weight percent to the weight of the
heat-expandable microspheres.

[0211] The maximum expansion ratio of heat-expandable microspheres is not
specifically restricted, but should preferably be at least 30 times, more
preferably at least 45 times, further preferably at least 56 times, still
further preferably at least 59 times, further more preferably at least 62
times, still further more preferably at least 65 times, and most
preferably at least 80 times. The upper limit of the maximum expansion
ratio of heat-expandable microspheres is 200 times.

[0212] The maximum expansion temperature of heat-expandable microspheres
is not specifically restricted, but should preferably be at least 240
deg. C., more preferably at least 250 deg. C., further preferably at
least 260 deg. C., further more preferably at least 270 deg. C., and most
preferably at least 280 deg. C. The upper limit of the maximum expansion
temperature of heat-expandable microspheres is 350 deg. C.

[0213] The heat-expandable microspheres of the present invention are
workable in a broad temperature range, which is understood with the curve
chart in FIG. 2. The procedure for making the curve chart is described
below in detail.

[0214] At first, the expansion-initiating temperature (Ts1) of
heat-expandable microspheres is measured (refer to the measurement of
expansion-initiating temperature in the Example), and a temperature
(T0) is optionally set at a point lower than Ts1 by 10 to 20 deg. C.
The heat-expandable microspheres are heated at a temperature which is
elevated from T0 to each of the predetermined heating temperatures
(T) and held there for 4 minutes. Then the true specific gravity (d) of
the microspheres after heating at each of the temperature is measured.
The heating temperature, T, can be set optionally, for example, several
temperatures being elevated from T0 by regular intervals, such as 10
deg. C.

[0215] Then the expansion ratio (E) of heat-expandable microspheres at a
heating temperature (T) is calculated by the following expression in
which the true specific gravity of the microspheres before heating is
represented as "d0" (refer to the measurement of the expansion ratio
in the Example).

E=d0/d (times)

[0216] The heating temperature (T) for microspheres is plotted on the
x-axis and the expansion ratio (E) of the microspheres is plotted on the
y-axis. Then the maximum of E is read to be defined as the maximum
expansion ratio (Emax). The maximum expansion ratio (Emax) can
be calculated by the following expression from the minimum true specific
gravity (dmin) which is read in a graph where the heating
temperature (T) for the microspheres is plotted on the x-axis and the
true specific gravity (d) of the microspheres is plotted on the y-axis
(refer to the measurement of the expansion ratio in the Example.).

Emax=d0/dmin (times)

[0217] Then the curve chart (FIG. 2) is drawn by connecting the points set
by plotting the heating temperature (T) for the microspheres on the
x-axis and the expansion ratio (percent) of the microspheres defined as
(E/Emax)×100 on the y-axis. The curve chart represents the
relation between the heating temperature (T) for heat-expandable
microspheres and the expansion ratio (E/Emax×100) of the
microspheres when the microspheres are heated and expanded.

[0218] A temperature range (δT), in which heat-expandable
microspheres of the present invention being heated for 4 minutes can
expand to at least 50 percent of their maximum expansion ratio in
4-minute heating, should preferably be at least 30 deg. C., more
preferably at least 40 deg. C., and further preferably at least 45 deg.
C. The δT can be defined as δT=T2-T1 where T1 is the lowest
temperature and T2 is the highest temperature at which heat-expandable
microspheres being heated for 4 minutes expand to at least 50 percent of
their maximum expansion ratio as shown in FIG. 2. The temperature range,
δT, indicates whether heat-expandable microspheres exhibit stable
expansion performance in a broad temperature range or not. A molding
composition which contains heat-expandable microspheres of the present
invention having large δT is workable in a broad temperature range
and will exhibit stable expanding behavior in molding processes even with
variable molding temperature. The maximum of δT is 100 deg. C.
Heat-expandable microspheres having a δT smaller than 30 deg. C.
may result in unstable expanding behavior in resin molding.

[0219] The range of T1 mentioned above is not specifically restricted, but
should preferably be at least 200 deg. C., more preferably at least 220
deg. C., further preferably at least 240 deg. C., and most preferably at
least 260 deg. C. The upper limit of T1 is 350 deg. C.

[0220] The range of T2 mentioned above is not specifically restricted, but
should preferably be at least 240 deg. C., more preferably at least 260
deg. C., further preferably at least 280 deg. C., and most preferably at
least 300 deg. C. The upper limit of T2 is 400 deg. C.

[0221] The heat-expandable microspheres of the present invention are
workable over a long period. For example, the heat-expandable
microspheres of the present invention exhibit stable and sufficient
expansion performance at high temperature in resin molding not being
influenced by the holding time in a cylinder of a molding machine, owing
to its longer working life than that of conventional heat-expandable
microspheres (refer to FIG. 12).

[0222] The working life mentioned here means a time range within which
heat-expandable microspheres remain to be workable under heating at a
high temperature such as a temperature between the expansion-initiating
temperature and maximum expansion temperature of the microspheres.
Heat-expandable microspheres subjected to high temperature are apt to
lose their workability due to the migration of the blowing agent
encapsulated therein. Thus the working life can be determined by
measuring the time-dependent weight loss of heat-expandable microspheres
heated at a temperature between their expansion-initiating temperature
and maximum expansion temperature.

[0223] Heat-expandable microspheres are usually known to contain water
which derives from the production process of the microspheres. Such water
contained in heat-expandable microspheres evaporates at the initial stage
of heating in the measurement of the weight loss of the heat-expandable
microspheres mentioned above. The weight loss of the heat-expandable
microspheres caused by the water evaporation, not by the migration of a
blowing agent, is not ignorable, and the weight loss the heat-expandable
microspheres must be measured considering the weight loss caused by the
water evaporation. The method for measuring the weight loss of
heat-expandable microspheres is described below in detail, on the premise
of the water evaporation.

[0224] At first, the weight loss of heat-expandable microspheres is
explained. The expansion-initiating temperature (Ts1) and maximum
expansion temperature (Tmax1) of heat-expandable microspheres are
measured prior to the measurement of the weight loss (refer to the
explanation in the Example). Heat-expandable microspheres are usually
processed in a temperature range between their expansion-initiating
temperature (Ts1) and maximum expansion temperature (Tmax1). Thus the
weight loss of heat-expandable microspheres is measured at a temperature
(Th) determined by averaging Ts1 and Tmax1.

Th=(Ts1+Tmax1)/2

[0225] The range of "Th" is not specifically restricted, but should
preferably be at least 150 deg. C., more preferably at least 180 deg. C.,
and further preferably at least 200 deg. C. The upper limit of "Th"
should preferably be 350 deg. C. If "Th" is lower than 150 deg. C., the
water evaporation may greatly influence on the weight loss measurement of
heat-expandable microspheres.

[0226] The weight loss of heat-expandable microspheres which are heated at
the heating temperature (Th) for "t" minutes, LWt (percent), can be
calculated by the following expression where the weight of the
microspheres (heat-expandable microspheres) before heating is represented
by W0, and the weight of the microspheres after heating at the
heating temperature (Th) for "t" minutes is represented by Wt (refer
to the calculations for the weight loss coefficient (WL) and the weight
loss ratio in 30-minute heating (percent) described in the Example).

LWt=(W0-Wt)/W0×100 (percent)

[0227] A curve chart (FIG. 13) can be drawn by connecting points set by
plotting the heating time ("t" minutes) for microspheres on the x-axis
and plotting the weight loss of the microspheres (LWt) on the
y-axis. The curve chart represents the relation between the heating time
("t" minutes) and weight loss (LWt) of heat-expandable microspheres
heated and expanded. The heating time can be set optionally, for example,
every 5 minutes except the initial 5 minutes to avoid the influence by
water evaporation which intensely occurs at the initial stage of heating.

[0228] Then the weight loss coefficient (WL) of heat-expandable
microspheres is defined by the following expression to determine the
length of the working life of the microspheres.

WL=(LW30-LW5)/CR

(where "LW5" represents the weight loss (percent) of the
heat-expandable microspheres after 5-minute heating; "LW30"
represents the weight loss (percent) of the heat-expandable microspheres
after 30-minute heating; and CR represents the retention ratio (percent)
of the blowing agent encapsulated in the heat-expandable microspheres.)

[0229] "Th" is usually higher than 100 deg. C., the boiling point of
water, and the water in heat-expandable microspheres is estimated to have
almost evaporated after heating the microspheres at "Th" for 5 minutes.
Thus the difference between the weight losses after 5-minute heating and
30-minute heating can be estimated to be the amount of the blowing agent
migrating out of the microspheres. For the purpose of compensating the
influence by the retention ratio of the blowing agent encapsulated in the
microspheres on the difference between the weight losses mentioned above,
the weight losses mentioned above is divided by the retention ratio of
the blowing agent encapsulated in the microspheres, and the result is
defined to be the weight loss coefficient (WL).

[0230] The weight loss coefficient (WL) of heat-expandable microspheres is
not specifically restricted, but should preferably be not greater than
0.45, more preferably not greater than 0.40, further preferably not
greater than 0.35, further more preferably not greater than 0.30, and
most preferably not greater than 0.25. The lower limit of the weight loss
coefficient of heat-expandable microspheres is 0. Heat-expandable
microspheres having a weight loss coefficient within the range mentioned
above has long working life, and a composition containing the
heat-expandable microspheres exhibits stable expanding behavior in
molding operation even if the molding time is variable. Heat-expandable
microspheres having a weight loss coefficient greater than 0.45 may fail
to stabilize the expanding behavior of a resin composition containing the
microspheres in molding operation. The working life of heat-expandable
microspheres can be evaluated by the weight loss ratio in 30-minute
heating (percent) as defined below.

Weight loss ratio in 30-minute heating
(percent)=(LW30/WG)×100

(where "LW30" represents the weight loss (percent) of
heat-expandable microspheres after 30-minute heating; and WG represents
the sum of the moisture content (percent) and the retention ratio of the
blowing agent (percent) encapsulated in the microspheres before heating)

[0231] The weight loss ratio in 30-minute heating is not specifically
restricted, but should preferably be not greater than 95 percent, more
preferably not greater than 90 percent, further preferably not greater
than 85 percent, further more preferably not greater than 80 percent, and
most preferably not greater than 75 percent. The lower limit of the
weight loss ratio in 30-minute heating is 5 percent.

[0232] The heat-expandable microspheres of the present invention should
preferably be wet with a liquid. The wetting is described above.

[0233] The hollow particulates of the present invention can be produced by
heating and expanding the heat-expandable microspheres mentioned above
and/or heat-expandable microspheres produced in a production process for
heat-expandable microspheres. The heating and expanding method is not
specifically restricted, and can include dry thermal expansion methods
and wet thermal expansion methods.

[0234] The examples of the dry thermal expansion methods are those
described in JP A 2006-213930, especially, the injection method. Other
dry thermal expansion methods are those described in JP A 2006-96963. The
examples of the wet thermal expansion methods are those described in JP A
62-201231.

[0235] The particle size of hollow particulates is not specifically
restricted, but should preferably range from 1 to 1000 μm, more
preferably from 5 to 800 μm, and further preferably from 10 to 500
μm. The coefficient of variation, CV, of the particle size
distribution of hollow particulates is not specifically restricted, but
should preferably be not greater than 30 percent, more preferably not
greater than 27 percent, and further preferably not greater than 25
percent.

[0236] The composition of the present invention includes at least one
particulate material selected from the group consisting of
heat-expandable microspheres of the present invention, heat-expandable
microspheres produced in the production process of the present invention,
and hollow particulates of the present invention; and a base component.

[0241] The formed product of the present invention can be manufactured by
forming the composition. The formed product of the present invention
include, for example, formed articles and formed materials such as
coatings. The formed product of the present invention has improved
properties including, light weight property, porousness, sound
absorbency, thermal insulation property, low thermal conductivity, low
dielectric constant, design, shock absorption and strength.

[0242] A formed product containing an inorganic compound can be processed
into ceramic filters, etc. by calcination.

EXAMPLE

[0243] The heat-expandable microspheres of the present invention are
specifically explained with the following Examples, though the present
invention is not restricted within the scope of the Examples. In the
following Examples and Comparative examples, "percent" means "weight
percent" unless otherwise specified.

[0244] The properties and performances of the base-material microspheres
and heat-expandable microspheres described in the following Examples of
production, Examples and Comparative examples were measured and evaluated
in the methods described below. Hereinafter the base-material
microspheres and heat-expandable microspheres may be sometimes referred
to as "microspheres" for simplifying the description.

[0245] [Determination of Average Particle Size and Particle Size
Distribution]

[0246] A laser diffraction particle size analyzer (HEROS & RODOS,
manufactured by SYMPATEC) was employed as the device for the
determination. Microspheres were analyzed in dry system with a dry
dispersion unit, where the dispersion pressure was controlled at 5.0 bar
and the degree of vacuum was controlled at 5.0 mbar. The median particle
size (D50 value) was determined as an average particle size.

[0247] [Determination of the Moisture Content of Microspheres]

[0248] The moisture content was determined with a Karl Fischer moisture
meter (MKA-510N, produced by Kyoto Electronics Manufacturing Co., Ltd.).

[0249] [Determination of the Retention Ratio of a Blowing Agent
Encapsulated in Microspheres]

[0250] One gram of microspheres were placed in a stainless steel
evaporating dish (15 mm deep and 80 mm in diameter), and weighed out
(W1). Then 30 ml of DMF was added to disperse the microspheres
uniformly. After being left for 24 hours at room temperature, the
microspheres were dried at 130 degree. C. for 2 hours under reduced
pressure, and the dry weight (W2) was determined. The retention
ratio of the encapsulated blowing agent (CR) was calculated by the
following expression.

[0251] (The moisture content in the expression was determined by the
method described above.)

[0252] [Determination of True Specific Gravity]

[0253] The true specific gravity of heat-expandable microspheres and
hollow particulates produced by thermally expanding the heat-expandable
microspheres were determined in the following method.

[0254] The true specific gravity was determined in the liquid substitution
method (Archimedean method) with isopropyl alcohol in an atmosphere at 25
deg. C. and 50% RH (relative humidity).

[0255] Specifically, an empty 100-ml measuring flask was dried and weighed
(WB1), then isopropyl alcohol was poured into the weighed measuring
flask to accurately form meniscus, and the measuring flask filled with
isopropyl alcohol was weighed (WB2).

[0256] The 100-ml measuring flask was then emptied, dried, and weighed
(WS1). The weighed measuring flask was then filled with about 50 ml
of microspheres, and the measuring flask filled with the microspheres was
weighed (WS2). Then isopropyl alcohol was poured into the measuring
flask filled with the microspheres to accurately form meniscus without
taking bubbles into the isopropyl alcohol, and the flask filled with the
microspheres and isopropyl alcohol was weighed (WS3). The values,
WB1, WB2, WS1, WS2, and WS3, were introduced
into the following expression to calculate the true specific gravity (d)
of the microspheres.

d={(WS2-WS1)×(WB2-WB1)/100}/{(WB2-WB1)-(WS3-WS2)}

[0257] The true specific gravities of heat-expandable microspheres and
hollow particulates were calculated in the above-mentioned method.

[0258] [Determination of the Expansion Ratio of Microspheres]

[0259] A flat 12-cm long, 13-cm wide, and 9-cm high box was made of
aluminum foil, and 1.0 g of microspheres were placed in the box
uniformly. Then the microspheres were heated at a prescribed temperature
for 4 minutes in a Geer oven, and the true specific gravity of the heated
microspheres was determined. The expansion ratio (E) of the microspheres
was calculated by dividing the true specific gravity (d0) of the
microspheres before heating by the true specific gravity (d) of the
heated microspheres. The maximum expansion ratio (Emax) is the
expansion ratio of the microspheres which have expanded to the maximum.

[0260] [Determination of the Amount of a Metal of the Groups from 3 to 12
in the Periodic Table Contained in Microspheres]

[0261] The decomposition of microspheres were carried out by placing 0.1 g
of microspheres and 5 ml of nitric acid (reagent for detecting hazardous
metals, produced by Wako Pure Chemical Industries, Ltd.) in a quartz
vessel and treating them with a microwave wet digestion system
(Multiwave, produced by Anton Paar) through the following steps 1 to 4 in
the order.

[0262] Step 1: treatment with the output power of 300 W for 4 minutes

[0263] Step 2: treatment with the output power starting from 400 W and
elevated to 600 W at the rate of 33.3 W/min for 6 minutes

[0264] Step 3: treatment with the output power starting from 700 W and
elevated to 800 W at the rate of 3.3 W/min for 30 minutes

[0265] Step 4: cooling down for 20 minutes without the output power

[0266] The resultant sample from the digestion was analyzed with an ICP
optical emission spectrometer (ICPS-8100, produced by Shimadzu
Corporation) to determine the amount of a metal of the Group 3 to 12 in
the Periodic Table being contained in the sample. The result was
calculated into the amount (weight percent) of the metal of the Group 3
to 12 in the Periodic Table being contained in the microspheres. The
amount (weight percent) of the metal of the Group 12 in the Periodic
Table was also calculated. In the tables below, the amount of the metals
lower than a detectable limit (usually less than about 100 ppm) was
expressed as "ND". In the Examples and Comparative examples, only the
metals derived from the metal-containing organic compounds or metal
compounds used for microspheres were detected.

[0267] [Determination of the Ratio of DMF (N,N-Dimethyl
Formamide)-Insoluble Matter]

[0268] In a glass vessel (36 mm in inside diameter) conditioned to a
constant weight (WP0), 1 g of microspheres and 29 g of DMF were
placed and shaken at 25 deg. C. for 24 hours (with a desktop shaker,
NR-30, produced by Taitec Co., Ltd., at a shaking rate of 15 min-1).
The mixture was separated with a desktop cooling centrifuge (produced by
Kokusan Co., Ltd., H-3R, with a RF-110 rotor and MC-110 bucket, at the
rate of 3500 rpm, at 15 deg. C., for 1 hour). Then the supernatant liquid
was removed and the gel in the glass vessel was vacuum-dried and
solidified at 130 deg. C. for 1 hour. The dried gel in the glass vessel
was transferred to a desiccator containing silica gel to be cooled down
to room temperature. The weight (WP2) of the glass vessel containing
the dried gel was measured, and the ratio of DMF-insoluble matter (WP)
was calculated by the following expression.

WP=WP2-WP0

[0269] The weight of the polymer (WP1) in 1 g of the microspheres was
calculated by the following expression from the retention ratio of the
blowing agent encapsulated in the microspheres (percent) and the moisture
content (percent) of the microspheres determined in the methods mentioned
above.

[0270] Then the ratio of DMF-insoluble matter (weight percent) of the
microspheres was calculated by the following expression from the weight
of the polymer (WP1) and the ratio of DMF-insoluble matter (WP) in 1
g of the microspheres.

[0272] Those temperatures were determined with a DMA (a kinetic
viscoelasticity measuring device: DMA Q800, manufactured by TA
Instruments). In an aluminum cup 4.8 mm deep and 6.0 mm in diameter (5.65
mm in inside diameter), 0.5 mg of heat-expandable microspheres were
placed, and the cup was covered with an aluminum cap 0.1 mm thick and 5.6
mm in diameter to prepare a sample. The sample was subjected to the
pressure of 0.01 N with the compression unit of the device, and the
height of the sample was measured. The sample was then heated at a
temperature elevated at a rate of 10 deg. C./min in the range from 20 to
300 deg. C., being subjected to the pressure of 0.01 N with the
compression unit, and the vertical change of the position of the
compression unit was measured. The temperature at which the compression
unit started to change its position to the positive direction was
determined as the expansion-initiating temperature (Ts1), and the
temperature at which the compression unit indicated the greatest change
was determined as the maximum-expansion temperature (Tmax1).

[0273] [Determination of the Expansion-Initiating Temperature (Ts2) and
Maximum Expansion Temperature (Tmax2) of Microspheres after being
Dispersed in Deionized Water]

[0274] A mixture prepared by adding 5 parts by weight of microspheres to
100 parts by weight of deionized water was shaken for 30 minutes to
disperse the microspheres. Then the microspheres were filtered and dried.
The expansion-initiating temperature (Ts2) and maximum expansion
temperature (Tmax2) of the microspheres after the dispersion were
determined as mentioned above.

[0275] [Calculation of the Range of Variation in Expansion-Initiating
Temperature (ΔTs) and the Range of Variation in Maximum Expansion
Temperature (ΔTmax)]

[0276] The range of variation in expansion-initiating temperature
(ΔTs) and the range of variation in maximum expansion temperature
(ΔTmax) of microspheres after dispersing the microspheres in
deionized water were calculated by the following expressions from Ts1,
Ts2, Tmax1 and Tmax2 of the microspheres determined as mentioned above.

ΔTs=(Ts1-Ts2)/Ts1×100

ΔTmax=(Tmax1-Tmax2)/Tmax1×100

[0277] In the following Examples of production and Examples, the
description, "an X-percent Y solution", means "a solution containing X
percent of Y".

[0278] [Determination of the Specific Gravity of a Formed Resin Product]

[0279] The specific gravity of a formed resin product was determined in
the liquid substitution method with a precision gravimeter, AX200,
produced by Shimadzu Corporation.

[0280] [Calculation of the Weight Loss Coefficient (WL) and the Weight
Loss Ratio after Heating for 30 Minutes]

[0281] In the box used for the determination of the expansion ratio of
microspheres, 1.0 g of heat-expandable microspheres were uniformly placed
and heated for "t" minutes at the average temperature (Th) of their
expansion-initiating temperature, Ts1, and maximum expansion temperature,
Tmax1. Then the weight of the heated microspheres (We) was measured to
calculate their weight loss, LWt (percent), by the following
expression. The weight loss, LW5, in the case that "t"=5 and the
weight loss, LW30, in the case that "t"=30 were calculated to
calculate the weight loss coefficient of the microspheres, WL. In the
expression, CR represents the retention ratio of the blowing agent
(percent) encapsulated in the microspheres.

LWt=(W0-Wt)/W0×100 (percent)

WL=(LW30-LW5)/CR

[0282] The weight loss ratio (percent) after heating for 30 minutes was
calculated by the following expression from the LW30 mentioned above
and the sum (WG) of the moisture content (percent) and the retention
ratio of the blowing agent (percent) of the microspheres.

Weight loss ratio after heating for 30 minute
(percent)=(LW30/WG)×100

[0283] [Example of Production 1]

[0284] An aqueous dispersion medium was prepared by adding 150 g of sodium
chloride, 70 g of colloidal silica containing 20 weight percent of
silica, 1.0 g of polyvinyl pyrolidone and 0.5 g of ethylenediamine
tetraacetic tetrasodium salt to 600 g of deionized water and by
controlling the pH of the mixture in the range from 2.8 to 3.2.

[0285] On the other hand, an oily mixture was prepared by mixing 120 g of
acrylonitrile, 115 g of methacrylonitrile, 65 g of methacrylic acid, 1.0
g of 1,9-nonanediol diacrylate, 90 g of isooctane, and 8 g of a
50-percent di-sec-butyl peroxydicarbonate solution.

[0286] The aqueous dispersion medium and the oily mixture were mixed, and
the liquid mixture was dispersed into a suspension with a Homomixer (T.K.
Homo-mixer manufactured by Tokushu Kika Kogyou). Then the suspension was
transferred into a compressive reactor of 1.5-liter capacity, purged with
nitrogen, and polymerized at 60 deg. C. for 20 hours by agitating the
suspension at 80 rpm and controlling the initial reaction pressure at 0.5
MPa. After the polymerization, the liquid was filtered to separate the
base-material microspheres which were then dried. The properties of the
resultant base-material microspheres are shown in Table 1.

[0287] [Examples of Production 2 to 10]

[0288] Base-material microspheres were produced in the same manner as in
Example of production 1 except that the components and their amounts were
replaced with those shown in Table 1. The properties of the resultant
base-material microspheres are shown in Table 1.

[0289] The base-material microspheres produced in Examples of production 1
to 10 are respectively referred to as base-material microspheres (1) to
(10).

[0290] To the liquid after the polymerization in Example of production 1,
55 g of an 80-percent diisopropoxytitanium bis(triethanol aminate)
solution, as a metal-containing organic compound, was added with
agitation at room temperature. The resultant dispersion mixture was
transferred into a compressive reactor (1.5-liter capacity), purged with
nitrogen, and processed at 80 deg. C. for 5 hours by agitating the
mixture at the rate of 80 rpm and controlling the initial reaction
pressure at 0.5 MPa. The resultant product was filtered and dried to
obtain heat-expandable microspheres. The properties of the microspheres
are shown in Table 2.

Examples 2 to 9, and 17, and Comparative Examples 4 and 6

[0291] Heat-expandable microspheres were produced in the same manner as in
Example 1 except that the liquid after the polymerization,
metal-containing organic compounds (metal compounds in Comparative
example 4 and 6) and their amounts were replaced with those shown in
Tables 2 to 4. The properties of the resultant heat-expandable
microspheres are shown in Tables 2 to 4.

Example 10

[0292] The liquid after the polymerization in Example 4 was filtered to
separate the base-material microspheres which were then dried. The
base-material microspheres in an amount of 400 g were uniformly
re-dispersed in 800 g of deionized water, and 15 g of an 80-percent
diisopropoxytitanium bis(triethanol aminate) solution was added with
agitation at room temperature as a metal-containing organic compound. The
resultant dispersion mixture was transferred into a compressive reactor
(1.5-liter capacity), purged with nitrogen, and processed at 80 deg. C.
for 5 hours by agitating the mixture at the rate of 80 rpm and
controlling the initial reaction pressure at 0.5 MPa. The resultant
product was filtered and dried to obtain heat-expandable microspheres.
The properties of the microspheres are shown in Table 2.

Examples 11 to 14, and 18

[0293] The heat-expandable microspheres were produced in the same manner
as in Example 10 except that the base-material microspheres, and
metal-containing organic compounds and their amounts were replaced with
those shown in Tables 2 to 4. The properties of the resultant
heat-expandable microspheres are shown in Tables 2 and 4.

Comparative example 1

[0294] The polymerization was carried out in the same manner as that in
Example of production 1 except that 55 g of a 80-percent
diisopropoxytitanium bis(triethanol aminate) solution was added as a
metal-containing organic compound to the liquid mixture of the aqueous
dispersion medium and oily mixture. However, the ingredients solidified
in the reaction and heat-expandable microspheres could not be produced.

Comparative Examples 2, 3 and 5

[0295] The polymerization was carried out in the same manner as that in
Comparative example 1, except that the liquid mixtures for
polymerization, and the metal compounds and their ratio were replaced
with those shown in Table 3. In Comparative examples 2, 3 and 5,
heat-expandable microspheres were produced contrary to the polymerization
in Comparative example 1 in which heat-expandable microspheres could not
be produced. The properties of the microspheres are shown in Table 3.

[0296] In Comparative examples 1 to 3 and 5, heat-expandable microspheres
were produced in polymerization in the presence of metal compounds and
the surface of base-material microspheres was not treated.

Example 15

[0297] Fifty grams of a 67-percent dioctyloxytitanium bis(octylene
glycolate) solution was sprayed to 400 g of the base-material
microspheres (with 2.6-percent moisture content) produced in Example of
production 4 which were being agitated, and the agitation was continued
for 30 minutes. Then the mixture was heated at 80 deg. C. for 3 hours,
and dried at 80 deg. C. in a reduced-pressure drier to be produced into
heat-expandable microspheres. The properties of the microspheres are
shown in Table 4.

Example 16

[0298] Four hundred grams of the base-material microspheres (with
2.6-percent moisture content) produced in Example of production 4 was
fluidized and agitated in a 10-liter fluidized bed, 47.5 g of a
50-percent titanium butoxy dimer solution was sprayed to the
microspheres, and the fluidization and agitation were continued for 30
minutes. Then the mixture was heated at 80 deg. C. for 1 hour, and dried
at 80 deg. C. in a reduced-pressure drier to be produced into
heat-expandable microspheres. The properties of the microspheres are
shown in Table 4.

[0299] The base-material microspheres produced in Examples of production 1
to 10 are respectively referred to as base-material microspheres (1) to
(10). The heat-expandable microspheres produced in Examples 1 to 18 are
respectively referred to as microspheres (1) to (18). The heat-expandable
microspheres produced in the Comparative examples 1 to 6 are respectively
referred to as Comparative microspheres (1) to (6).

[0300] In Tables 2 to 4, the contents of the cells belonging to the
horizontal row titled with "Base-material microsphere" and to the
vertical columns titled with "Examples 1 to 9 and 17 and Comparative
Examples 4 and 6" specify the Examples of production in which the liquids
containing base-material microspheres were prepared; the contents of the
cells belonging to the same horizontal row and to the vertical columns
titled with "Examples 10 to 14 and 18" specify the Examples of production
in which the base-material microspheres were produced; and the contents
in the cells belonging to the same horizontal row and to the vertical
columns titled with "Comparative examples 1 to 3 and 5" specify the
Examples of production in which the liquids for the polymerization were
employed.

[0301] In Tables 2 to 4, the description of "continuously after
polymerization" in the cells belonging to the horizontal row titled with
"Time of addition" means that a metal-containing organic compound (a
metal compound in each of Comparative examples 4 and 6) was added to the
liquids after the polymerization in the Examples of production. The
description of "after re-dispersion" in the cells belonging to the same
horizontal row means that base-material microspheres produced in the
polymerization in the Examples of production are separated and
re-dispersed in deionized water and a metal-containing organic compound
was added to the dispersion. The description of "before polymerization"
in the cells belonging to the same horizontal row means that a metal
compound was added to a liquid mixture prepared by mixing an aqueous
dispersion medium and oily mixture in the Examples of production. The
description of "after drying" means that a metal-containing compound was
added to base-material microspheres after drying. The description of "at
fluidized bed" means that a metal-containing compound was added to dried
base-material microspheres at fluidized bed.

[0302] [Workable Temperature Range of Heat-Expandable Microspheres]

[0303] In a box used for the determination of the expansion ratio of
microspheres, 1.0 g of the microspheres (5) produced in Example 5 was
weighed and uniformly placed. Eight boxes each containing 1.0 g of the
microspheres (5) were prepared and heated in a Geer oven at different
temperature levels shown in Table 5 for 4 minutes. The true specific
gravity and expansion ratio of the resultant hollow particulates
(thermally expanded heat-expandable microsphere) were determined.

[0304] The base-material microspheres (3) produced in Example of
production 3 were thermally expanded in the same manner as mentioned
above, and the true specific gravity and expansion ratio of the resultant
hollow particulates were determined.

[0305] The only difference between the microspheres (5) and base-material
microspheres (3) is their surface treatment. The base-material
microspheres (3) have similar properties to the microspheres of the
Comparative examples from the viewpoint of the present invention. The
results from the determination are shown in Table 5.

[0306]FIG. 3 is a graph showing the result from the determination of the
true specific gravity of the surface-treated microspheres (5) and the
base-material microspheres (3) without surface treatment at varied
heating temperatures. The graph shows that the microspheres (5) resulted
in lower true specific gravity than the base-material microspheres (3) in
almost all of the regions of the heating temperature. The true specific
gravity of the base-material microspheres (3) increased with the increase
of heating temperature in the high temperature region above 240 deg. C.
due to the migration of the blowing agent out of the microspheres, while
the true specific gravity of the microspheres (5) remained low with
slight variation even in the high temperature region above 240 deg. C.

[0307]FIG. 4 is a graph showing the result from the determination of the
expansion ratio of the microspheres (5) and base-material microspheres
(3) at varied heating temperature. The graph shows that the surface
treatment contributes to stable expansion performance of microspheres in
high temperature region.

[0308]FIG. 5 is a graph showing the relation between the heating
temperature for the microspheres (5) and base-material microspheres (3)
and their expansion ratio. The graph was drawn in the same manner as that
in FIG. 2 mentioned above. The δT of the base-material microspheres
(3), δTA, and the δT of the microspheres (5),
δTB, were respectively read to be 26 deg. C. and 48 deg. C. in
FIG. 5. This proves that the working temperature range of the
microspheres (5) is much broader than that of the base-material
microspheres (3).

[0309] The microspheres and base-material microspheres produced in the
Examples described above were heated and expanded, and the relation
between the heating temperature and their expansion ratio was plotted and
drawn into the graphs of FIGS. 6 to 11 in the same manner as that for
FIG. 5. The δTs read in each of the graphs are shown in Tables 1
and 2. The results show that the heat-expandable microspheres produced in
the Examples have large δTs, which represents broad working
temperature ranges of the microspheres.

Example A1

[0310] Wet heat-expandable microspheres were prepared by uniformly mixing
500 g of the heat-expandable microspheres produced in Example 9 and 25 g
of a process oil (Kyoseki Process Oil P-200, produced by Nikkou Kyoseki
Co., Ltd.).

[0311] Then 52.5 g of the wet heat-expandable microspheres and 2447.5 g of
a polystyrene (AGI02, having a density of 1.04 g/ml and MFR (melt flow
rate) of 15 g/10 min at 200 deg. C. with 5 kgf, produced by PS Japan
Corporation) were uniformly mixed. The mixture was filled in the
cylinders of a Labo Plastomill (ME-25, two-shaft extruder, produced by
Toyo Seiki Seisaku-Sho Co., Ltd.) equipped with a T-die (with 1.8-mm wide
lip) where the temperature of the cylinders C1, C2 and C3 and the T-die
was set at 230 deg. C. and the rotational speed of the screw was set at
25 rpm to hold the mixture in the cylinders for 12 minutes. Then the
screw was stopped for 5 minutes, 15 minutes, and 30 minutes respectively,
and after each stop the mixture was extruded with the screw rotating at
25 rpm to be formed into an expanded sheet. The specific gravities of the
expanded sheets formed after each screw-stop period are shown in Table 6.

[0312] The result in Table 6 shows that the specific gravities of the
expanded sheets are constant not being influenced by the periods of the
screw stop at high temperature, and it proves the long working life of
the microspheres. A composition containing such microspheres can be
constantly manufactured into expanded products without the influence by
the length of holding time in extrusion molding.

Comparative Example A1

[0313] Expanded sheets were manufactured in the same manner as that in
Example A1 except that the heat-expandable microspheres were replaced
with the heat-expandable microspheres produced in Example of production
4. The properties of the sheets are shown in Table 6.

[0314]FIG. 12 shows the comparison between the working lives of the
microspheres of Example A1 and Comparative example A1. The
heat-expandable microspheres of Example A1 exhibit long working life
indicated by the specific gravity of the expanded sheet which do not
change with the increase in the screw stopping time from 0 to 30 minutes.
On the contrary, the heat-expandable microspheres of Comparative example
A1 exhibit short working life indicated by the remarkable decrease in
their expansion performance and the gradual increase in the specific
gravity of expanded sheets with the increase in the screw stopping time
from 0 to 30 minutes.

[0316]FIG. 14 is a graph showing the relation between the heating time
and weight loss of the microspheres (9) used in Example A1 and the
heat-expandable microspheres used in Comparative example A1 (the
base-material microspheres (4) for producing the microspheres (9)). Those
microspheres were heated at 234 deg. C., which is the "Th" of the
microspheres (9). The graph was drawn in the same manner as that for the
curve chart in FIG. 13.

[0317]FIG. 14 provides the data for comparing the lengths of working
lives of those microspheres with and without the surface treatment.
Although the microspheres (9) and base-material microspheres (4) have the
same retention ratio of the blowing agent, the weight loss of the
base-material microspheres (4) reached to 17.5 weight percent after being
heated for only 10 minutes while the weight loss of the microspheres (9)
was about 17 weight percent after being heated for 30 minutes. In other
words, surface-treated heat-expandable microspheres result in smaller
weight loss and retain much longer working life than microspheres without
surface treatment, even after they are heated at high temperature for a
long time.

[0318] The weight loss coefficient and weight loss ratio in 30-minute
heating of the surface-treated microspheres and base-material
microspheres mentioned above were calculated and shown in Tables 1 to 3.
As mentioned above, the heat-expandable microspheres of the Examples have
a weight loss coefficient ranging from 0 to 0.45 and a weight loss ratio
in 30-minute heating ranging from 5 to 95 percent, and the data prove
that those microspheres have a long working life.

Example A2

[0319] In a box used for the determination of the expansion ratio of
microspheres, 1.0 g of the heat-expandable microspheres of Example 15 was
weighed and placed. The box was heated in a Geer oven at 240 deg. C. for
4 minutes. The resultant hollow particulates had a true specific gravity
of 0.025 g/ml.

[0320] Then 0.5 g of the hollow particulates was immersed in 30 g of
acetonitrile and kept for 60 minutes at an ambient temperature of 25 deg.
C. Then the hollow particulates were taken out, washed in normal hexane
and dried, and the true specific gravity of the hollow particulates was
determined to be 0.026 g/ml. The true specific gravity of the hollow
particulates hardly changed after the immersion in acetonitrile and it
proves that the hollow particulates have excellent solvent resistance as
well as the heat-expandable microspheres of Example 15.

Example B1

Preparation of a Master-Batch Pellet

[0321] A resin mixture was prepared by uniformly mixing 500 g of the
heat-expandable microspheres produced in Example 17 and 25 g of a process
oil (Kyoseki Process Oil P-200, produced by Nikkou Kyoseki Co., Ltd.),
adding 475 g of polyethylene pellet (DNDV0405R, produced by Dow Chemical
Japan) to the mixture, and uniformly mixing the mixture.

[0322] Then the resin mixture was thrown into a Labo Plastomill (ME-25,
two-shaft extruder, produced by Toyo Seiki Seisaku-Sho Co., Ltd.)
equipped with a strand die (with 1.5-mm hole diameter) through the
raw-material hopper of the Labo Plastomill. The mixture was knead in the
Labo Plastomill, where the temperature of the cylinders C1 and C3 and the
strand die was set at 150 deg. C., the temperature of the cylinder C2 was
set at 160 deg. C., and the screw speed was set at 40 rpm. Then the
mixture was extruded and processed with a pelletizer into a master-batch
pellet B1 (containing 50 weight percent of the heat-expandable
microspheres).

[0323] (Injection Molding)

[0324] A pellet mixture was prepared by mixing 6 parts by weight of the
master-batch pellet B1 and 100 parts by weight of polycarbonate resin
(TARFLON® R2200, having a specific gravity of 1.2, produced by
Idemitsu Kosan Co., Ltd.). The pellet mixture was fed to a screw-type
preplasticating injection molder (TUPARL TR80S2A, with 80-ton clamping
capacity, supplied by Sodick Co., Ltd.), melted, kneaded, and
injection-molded into a plate. The injection-molding was carried out with
a plasticizer temperature of 260 deg. C., injection speed of 70 mm/sec,
mold temperature of 80 deg. C. and injection temperature ranging from 260
to 320 deg. C. The expansion performance of the pellet mixture was
evaluated by determining the specific gravity of the resultant molded
products. The specific gravities of the molded products produced at each
molding temperature are shown in Table 7.

Example B2, and Comparative Examples B1 and B2

[0325] Molded products were produced by injection molding in the same
manner as that in Example B1 except that the heat-expandable microspheres
were replaced with those shown in Table 7. The specific gravities of the
molded products produced at each molding temperature are shown in Table
7.

[0326]FIG. 15 shows the plot of the specific gravity data of the products
produced in injection molding summarized in Table 7, in which the
expansion performances of the pellet mixtures of Examples B1 and B2 are
compared to that of the pellet mixtures of Comparative examples B1 and
B2.

[0327] The plot in FIG. 15 clearly shows the difference in expansion
performance depending on the surface treatment.

[0328] In Examples B1 and B2, the surface treatment on the base-material
microspheres including isohexadecane as a blowing agent achieved the
increase in the expansion-initiating temperature and extension in the
working temperature range of the base-material microspheres. On the
contrary, the microspheres without surface treatment in Comparative
examples B1 and B2 resulted in low retention of the encapsulated blowing
agent, low expansion ratio and narrow working temperature range of the
microspheres, though their expansion-initiating temperature was increased
owing to isohexadecane employed for the blowing agent.

[0329] In Tables 1 to 7 described above, the abbreviations in Table 8 are
employed.

[0330] The heat-expandable microspheres of the present invention have
excellent heat resistance and are employable in a broad range of molding
processes with high-melting-point resins. The heat-expandable
microspheres of the present invention also have excellent solvent
resistance and exhibit stable performance in paints, sealants and
adhesives for a long time.